Let us assume it profit motivated, and they've calculated their potential losses as a result of legalization (let's call it pl for potential lossses), they've calculated the probability of it passing without a $500k donation (let's call it pnd or probability no donation) and the probability of it passing with a $500k donation (pwd for probablity with donation). Then, they can make the following calculation:
If pl x pwd - pl x pnd > $500k then the $500k is money well spent. Otherwise it's a poor bet. This leads to interesting conclusions:
* Proposition 205 was close (51%-49%). So it seems likely small events could swing it * $500k is in context of a $3m campaign, so it seems again likely that their donation had an impact. But compare it to the 1 billion spent on the general election, and how many more people would be turning out because of the general election, it seems less likely it had an impact * I have no way of knowing what their potential losses are from legalisation, but let's assume they're high.
Let's say the difference between pwd and pnd is a 2.5% chance that their donation swung the election (which seems overly generous, elections usually aren't that easy to swing). That means they are assuming losses of approximately 20 million in Arizona from legalisation.
Generally though, I'm not convinced they made this analysis, and instead were trying to demonstrate that they were opposed.
(That said, for drugs I only use Dark Souls, coffee and a few beers now and then. Maybe a glass of wine sometimes, mostly because I am swayed by the health propganda.)
[2] Cannabidiol in development http://www.insysrx.com/products/in-development
http://www.azcentral.com/story/opinion/op-ed/ej-montini/2016...