Overpaid? Absolutely. Regretted a purchase? Never.
Though maybe the fact that I'm having to start over from nearly scratch may make that opinion change :/
Though I "buy for function" - rather than buying for value or to flip - so I won't pay more than what I feel a game is worth to enjoy, that way I never feel that buyer's remorse if I see it cheaper later (may not have gotten "the best deal", but having gotten "my money's worth").
Honestly what I end up regretting more often are sales - not purchases
(Trades are a weird spot, since I've had good and bad ones, but can't say I really "regret the trade", so much as regret having to hunt yet again for what I traded).