In regrads to beatmakers who sell the .mp3 at one price and the .wav at another price ... why?

I always wondered why some people require more money to sell something like that at a higher price. Wouldn't you want to attach your name with quality? Wouldn't it make sense to maybe just ditch the mp3 altogether and just sell the .wav? Do they charge higher because it's a bigger file size or takes longer to render or something?

If that song get's some traction, and they find out you produced it - they may not attach your name/image with quality.

It feels more like a mild money grab - like 'o i just want more money' or something.

I dont sell or buy beats, but this has crossed my mind.