Creativity is always good, but the point that makes me believe that this isn't really viable is the fact that every ditto encounter takes 5 turns instead of 3. That's just too long. In the long term, you'll spend less time (and mental energy) if you just set up one proper ditter farming mon that snowballs into enough money to set up better ones.
Your price estimates aren't particularly representative imo. Sure, you could spend 100k+ on a perfect Vaporeon, or you could breed a decent one yourself for less than 20k. Here, watch me do it with whatever is on the market rn, no crazy snipes or luck required:
I didn't roll particularly well on it, it still does up to 85 damage to a Hoenn Ditto at lvl 100 (the perfect Vaporeon would do 87), but that's literally a 2.3% difference and won't really affect catch rate. I've taken him along on my EV run, sending him your way shortly π