For members
A members' price on everything else you sell is the cheapest retention tool there is, and it costs nothing when nobody uses it.

Share it inside the membership; cap the uses if you want.
Email everyone currently subscribed from the dashboard.
When someone stops paying, they stop being a member.
No cut of the membership (on paid plans) or of what members buy.
0%
platform fee on any plan
~1 min
to claim a link and publish
10
product types on one page