I will say, however, that I agree that $20 for 10 spins is a ridiculous amount of money. I believe Ichumon did it at $10 for 10 spins, which seems more fair to me.
And if you're looking to get around any potential legal issues, mayhaps just turn them into $10 or $20 monthly item bundles that permanently retire, like your current Beta Supporter Bundles.
Or come up with a Premium membership that gives a user a monthly item. If a Premium user doesn't like that particular month's item, they'll sell it for potatoes and thus it'll be available to non-Premium folks, too.
Now that I think about it, re: Ichumon: They also had a Premium shop that sold the same items (albeit for higher pay-currency prices) every month. So maybe that's how they avoided legal issues re: gambling. ...Either that or no one ever cared enough to try to sue 'em, lol.