Wow. I think I misunderstood too and wrote a super dorky response.
To respond to your original thought and motive behind your OP, I think there is probably some of that: girls looking at the study and when they set their schedules or are deciding where to go in 3 weeks (i.e. Do I go to boston, NYC, or just stay home?) I am sure that, at the margin, Boston will win out every time. However, I'm not certain that girls read the article and say to themselves, I gotta get myself to Beantown -- the guys there seem really generous and the market is totally primed! When all things are relatively equal though, Boston is going to be incredibly appealing to touring providers.
If Boston were a city similar in beauty, culture, academia, history, and general atmosphere to a Flint, Michigan or a Gary, Indiana (and please please don't take offense if you love either city or call one home; I am just making a sweeping generalization and could be totally off. For one, Gary has a sweet state fair and Flint has produced some terrific ice hockey players!) then I think having a riper market and being able to command a marginally higher price may not sufficiently compensate for the other negatives about the city and I would still opt to go someplace else or just not tour at all.
And this brings me to my (I'm sure you're saying thankfully, haha) point: If a provider can regularly ask for $300 back at home in Alltown, USA, and she has found that the $300 price point enables her to fill up her calendar to include as many appointments as she would like to accept, with the city's average provider requested donation being $250, then going to Bayville, America, with it's provider average rate being $400, still won't allow her to jack up her requested hourly consideration to $500 and obtain the same results for booking. Or will it? (Ignore the other variables that might impact the bookings for our fictional provider here -- for example, her nonexistent or much smaller per existing client base or her novelty which might positively impact her bookings despite having no regulars there. It just gets too confusing trying to look at these.)
Because I have never toured and decided not to for the foreseeable future, I really don't know much about the pricing variations and the underlying rationale behind these shifts, but do most ladies alter their rates when touring? Is this solely to help cover the added costs of the travel, or is it also because the markets differ and therefore as demand increases so can asking rate?
Providers, do your considerations vary more granularly than this: Do you not only ask a different rate when at home versus when on tour but does the rate also differ from city to city when on your?
Do cost of living figures and projected expenses impact your pricing model from city to city more than your impression of the market's appetite for your provider "type", your perception of the given market's saturation level, or your general estimation of what you can reasonably charge in relation to similar providers in that city?
Are there any cities that are always challenging for you as a Provider? (For example, I am pretty sure I would be a total dud in LV; as much as I would LOVE to have that sexy and pin-up goddess look, I just don't and would likely be viewed as plain -- an everyday "basic bitch", if you will, hahahah)
Are there any cities that you feel have incredibly strong markets, in areas that you maybe didn't anticipate would have such a strong, even if underground, hobbyist representation there
TLDNR.
Technically, $600 per is way above cost for outcall only in this market, unless you have to overspend on advertising because the phone isn't ringing.
I don't know much about the research design or methodology used either and must confess that I merely skimmed the article for the few main takeaways, so I am hardly informed here, but assuming the study controlled for cost-of-living confounding variables that might impact accurate data analysis and subsequent evidence-supported findings, Boston providers must be extremely expensive then in relation to other cities.
A recent study's results suggested that the top threw most expensive cities in the country -- in terms of residential real estate costs per square foot (within the city limits only) -- are as follow:
San Francisco
Boston
New York City
Unfortunately, I don't remember the rank order of the remaining cities, but was surprised to see Boston ahead of NYC until I read the fine print footnoted at the bottom of the chart: New York City here includes all five boroughs, and the figure representing NYC's mean cost per square foot of residential real estate purchases blended with the average cost per square foot of residential rental properties accounts for the Bronx, Queens, Staten Island, and Brooklyn, as well as the much pricier Manhattan. When Manhattan is isolated and compared to the other American cities on its own, it is more expensive than Boston, albeit still "cheaper" than SF. ... And yes, of course, cheaper is being used ironically here! 
So, adjusting for the COL confounding variable when examining provider cost across major US cities likely doesn't later the results that substantially: SF likely has less expensive providers (although I have no empirical evidence or past personal research findings to support this assertion -- and it is mostly just based on personal experience browsing provider prodiles, talking with hobbyists and providers from the West Coast, and the "gut feeling" factor that often governs opinions far more than it really ever should), but even if they were the same, Boston's lower COL would have Boston topping SF in relative provider average donations.
NYC is interesting because I have always assumed their providers were spender than Boston's. Even if this is the case, the incremental cost of NYC Ladies has to be smaller than the COL difference between NYC and it's cheaper neighbor, allowing the researchers to conclude that Boston providers request more than NYC companions for their fabulous services and, of course, for their time. 
The one question mark likely on everybody's mind is Vegas. Again, I am not sure where Vegas sits on the list of expensive cities to live in, but if it is below Boston in COL and in average adjusted Provider rates, then the only possibility is that LV providers ask on average for smaller donations. I have a hard time believing this, and know that Vegas' top ladies have some seriously high rates. And they look to be worth every penny physically too! There are some seriously sexy escorts out there, even more so than in Boston, which is a hotbed for high-end and really fabulous providers.
I think the study is only questionable in relation to where it places Vegas' adjusted Provider rates, but if it takes the mean as opposed to the median (I used the term "average" very loosely in this post, referring to mean and median interchangeably as I wasn't sure which Measure of the "middle" was employed by the researchers) then there may be only a handful of really pricey ladies and a concentration of relatively inexpensive escorts who throw the "middle" off and create a skewed bell curve that peaks to the left -- the lower donation area of the four quadrants.
Where does DC stack up on the list?
And do we know how they accounted for ladies who offer 15 minutes versus those with two hour minimums? Do they look at cost per minute of service, which is an unrealistic and therefore unrepresentative figure for the purpose of this examination?
Did they look at mean or median? And most importantly did they remove outliers? Since I don't know any of this, I have only very dubious conclusions I can draw with any confidence.
Interesting nonetheless. We just have the most generous guys here clearly, men who know the value of an exceptional lady and unsurpassed service and attention. Go Boston!!
Posted By: PreppyGuy07
...that study was cost-of-living adjusted, so while there are more expensive cities on a per-hour basis, Boston is the most expensive on a relative basis. I don't know anything about their methodology, and therefore how accurate the conclusions, but Boston is expensive any way you look at it.
