In an era when you should be putting users first, you’re putting them last. Both your creators (since they now have to do something they don’t want to), and consumers (who'll be subject to more "spam"-quality listings).
How much do dormant user accounts really cost your platform? My guess is it’s pretty insignificant.
Waived if you contribute new products or referral sales every 15 months, and they stop charging them once your balance hits 0.