First off Suzanne, quite a meaty topic.
Well, using the model of how the pilot programs for legalization of cannabis is going in Washington State and Colorado, I'm going to take the side that donation rates would actually drop.
Here's the thing, again using the pilot programs of cannabis as a measuring stick, we've actually seen that the prices for cannabis have dropped and leveled out. In Colorado, dispensaries are popping up like Starbucks (all over the place) business is booming, supply has increased, therefore, prices have leveled off or dropped. In the cannabis industry this equals thinner margins - but it's still a huge business, so thin margins or not, there is a green rush that's going on in Colorado and Washington State.
Take that same model and apply it to the hobby, with widespread availability (and I know someone will argue about The Bunny Ranch prices, but that is not considered widespread availability) and the margins for profit will definitely change. No doubt there would be new business expenses that would need to be factored into the metrics, but when you throw the spin of widespread availability into the mix, that brings down the overall pricing. When the "taboo" factor is gone, the tried and true business model of supply and demand takes root.
But then again, that's just my .02 cents - I don't claim to be an economics professor at NYU Stern School of Business, so what do I know. LOL!
nyca