I can't think of a price raise like that happening to me.  I'd take it that it means she didn't feel the chemistry with you.  It doesn't always work out.  I get three types of reactions -- some bug me for future dates, I've gotten a future discount, some don't initiate second contact, but are agreeable, and some make excuses why they aren't available.  I would classify  a price increase in that last category, they're not that excited to do it again.  Spend your time on the first two categories.

This was several years ago.  I started dating a lovely girl I met on SA.  I think we went BCD all of twice, for the original price we had agreed upon.  Then she asked for double that amount and when I declined she said she was going to "pursue more lucrative opportunities". I never saw her again, but I did see her pop up on several escort sites!  Usually the original agreed price is what persists throughout the arrangement.  So it pays to negotiate with care.   One idea I learned here (but have never used yet) is that if you can't agree on an amount, you could offer her something higher than your original offer for the first time BCD together as a "signing bonus".  With the clear understanding that you will renegotiate after that first time.  If she agrees it gives you the opportunity to get your foot in the door (wait, wrong metaphor again!)  and impress the heck out of her in the bedroom so she will really want to see you again.  And if that doesn't work, at least you had a one and done with a hottie, which ain't a bad thing.

Never had the situation the OP suggested, and I concur that she is not into you.  Let her go.  

I have actually had Sweetman's second idea -- renegotiate after the first date -- work well on two different occasions.  One was a very hot 22-yer-old that lasted a year and was a legitimately solid arrangement like we all seek.   I really wanted her naked, and the first offer got her there.  She pursued the continuation of the arrangement (see Cat's DATY thread), offered the new arrangement, and we settled into an every other week pattern until she moved away.

The other was a nice hot woman, and again, a real desire to get her BCD -- ended up as good sex with no chemistry -- went from 300 to 250 and became an intermittent thing where I dropped her a line when I wanted to see her.  Saw her maybe five or six times over four years.  I think if I called her today, it would be 250.  Nothing special as a sugar arrangement, but I got good sex with a nice woman and a predictable outcome.  

I am pretty sure she had a good time. She has been bugging me to come back, but at $600. I think this relationship is over though as  (a)  I don't want to pay $600 and (b) I do not feel in control of the relationship.  The vibe is just wrong and seems to have been from the beginning.  Not worth the hassle.

I'm not a fan of renegotiating after the 1st BCD. Certainly, an SB may force the discussion, but as Ali2 notes, it means the issue of control is not settled.  I prefer to negotiate upfront with the assumption that we will have an ongoing arrangement, knowing that either of us can bail at any time (it is "no-strings" after all).  

 
So some observations/thoughts about this post:  
1. "Exclusive" is fantasy. We know it, she knows it. But she may want to offer it (falsely) as a negotiating tactic. She incorrectly assumes we will care about other dicks using her parts - and we don't; as long as she showers and gets tested, please. So acknowledge when she offers, but assume (and don't care) that it's a lie.
2. I did post about the power of good DATY. But that still lays (pun intended) on the foundation of cash paid for intimate time.  
3. Control is yours to keep or give away. You always have the power to say no. And you are correct to do so in this case, but...
4. There are a few approaches you can take IF you want to renegotiate your arrangement.  
A. Propose more frequent dates as a means to get more funds.  
B. Since she is focused on the cash, offer to drop the date extras like expensive dinners and gifts/shopping
C. Meet her half-way, then drop the date extras anyway.  
NOTE: Underlying all of these strategies you must base your proposals on YOUR BUDGET, not her "worth."  Never tell her she is not "worth" $600. Tell her your budget makes it difficult to commit to anything over $400 for an ongoing arrangement.  She will never agree she is worth less. Let her find a way to "fit" into your budget, and therefore you own the "control" valve for the arrangement.  

 
Finally, arrangements always end.  I suggest you not focus too hard (pun intended - again!) on keeping this one, as there will be new SB's in your area soon.  I'd rather have fond memories of a few great, hot, sloppy, wet, earth-shaking BCDs with one SB, than several memories of uncomfortable, awkward, is-THIS-really-worth-an-extra-$200-when-there's-a-sweet-18-23-year-old-hottie-I-could-be-banging-for-less moments.  

 
Life is good

 
The Cat

It happened to me once, after seeing a very sexy girl a few times.  Suddenly it went from $400 to $600.  I took it to mean she didn't like me, or wasn't attracted to me, or whatever.  I said a respectful "you can ask whatever you want" and then said goodbye.

Hit it off chatting on platform with a 20yo AA spinner on the east coast. She readily switched to text where we discussed details. She said she wanted a ppm of 700 *plus* 3k per month! Haha. I told her 500 ppm and she immediately agreed. She then clarified to make sure I understood the 500 ppm was fine without the extra 3k per month allowance. (Uh, yeah, the additional allowance was never in the cards.)

 
We confirmed everything we like and don't like in the bedroom. And she volunteered four hours! Game on, date set for tomorrow, and good night until morning.  

 
Then, first thing in the morning I wake up to a long text lecturing me about how she's no prostitute, she looked up my net worth and I can afford far more than 500 and she even found a middle finger emoji with which to salute me. The topper was if I was agreeable to her original proposal of 700ppm + 3k/month, then everything's good.

 
So of course we don't burn bridges here (right, HTC?), so I responded with as much kindly politeness and wisdom as I could muster and ... crickets of course. Hahaha!