Consider a scenario where you can spend $1000 to have a 50% shot of winning $2500. It's a definite win

Not true; $2500 is not necessarily 2.5 times as useful as $1000.

http://en.wikipedia.org/wiki/Marginal_utility#Diminishing_marginal_utility

People overcome innate but undesired drives all the time, like committing violence out of anger. Your former approach actually doesn't sound very hard to me, although it might be hard for someone unusually loss-averse. Also, the latter approach sounds like it might not be self-deception in every sense, since there's no single thing in the mind that is a "belief" (q.v. Instrumental vs. Epistemic – A Bardic Perspective); it seems like this point is being consistently ignored throughout this discussion.