Huh. If I used that logic I wouldn't own any games!
Yeah, but most of those $100 games that I buy aren't essentially duplicating things I already have.
If I want to play a B/X-style game, I'll grab one of my 3 original Rules Cyclopedias, or one of the 4 red Ottus books or my 3 blue Ottus books, or one of my full set of Mentzer BECMI rules and just play those.
And if not that, I've got 3 different editions of C&C, a shit-ton of old 1e AD&D, a slightly smaller (crap-ton?) of 2e AD&D, 4 different intro-level BECMI-series box sets, 3 different DCC starter books, and that's just what's in the D&D "family" of games, without getting into any other rules systems.