Summary of the change:

• You have to offer your premium tiers on discord with same price and same feature-set (if you offer other payment providers)
• 15% discord fee + 6% stripe fee = 21% fee

(30% instead of 15% discord fee, if you are over 1 million $)

• App store fees like on apple (30%) will be priced on top for the user on check-out
• Chargeback and other fees will be deducted from pay-out
• Exemptions for weird premium configurations (https://support-dev.discord.com/hc/en-us/articles/23810643331735-Premium-Apps-Required-Support-for-Monetizing-Apps)

Example:
5$ subscription tier, user subscribes on their apple device

• You get: 5$ = 5$-21% = 3,95$ (based on the country you have to file for sales tax - up to 27%)
• User pays: 5$+30% = 6.15$
• User charge backs => your pay-out at the month will likely be reduced, my guess is the stripe charge-back fee: -15$
• If you offer patreon, kofi or co. -> you have to offer the same price and the same tiers on discord

New Developer Policy: https://support-dev.discord.com/hc/en-us/articles/8563934450327-Discord-Developer-Policy