First of all, discovering a betting strategy that enables you to win 80% of your bet isn't something that's easy or something we see all the time so if I'm able to discover something like that, someone is willing to pay me to have access to my strategy, i see no reason why I'd keep it to myself.
Ordinarily, I'm not the kind of person that hides or keep success to myself, I'd normally give share it to my friends for free so seeing someone who'd be willing to pay me for what I can be able to give out for free is a bonus for me. So yes I wouldn't mind selling my strategy for good sum.