Thanks for the input
1. I highly doubt people will bother genning dex fillers etc. to be sold at the 20PC price point, when they could be spending their time selling at 60PC. The whole point of this system is to benefit the non-genners. It shouldn't affect the genners at all.
2. It doesn't matter if they're really breeding or not. As long as the people selling customs for 60PC aren't affected by the price change, it doesn't matter. As far as the second argument goes, people on the site could currently lie and say they're "trading" at any time. Some things just can't be managed, you have to hope the members are at least somewhat honourable. To add to that, why would someone bother selling a BR Pokemon for 20PC when the rule is 60PC? They will just make less credits. And if they're hoping to establish a monopoly by doing that, they will quickly be caught by staff.
3. This will not affect anyone selling custom Pokemon. And tbh, anyone selling far above the 60PC min is already losing a ton of their business. This may actually give them something else to sell besides custom Pokemon, if they're too proud to lower their prices.