Is there some sort of cache back for a working fp3 when ordering a fp5?
Yes there is, but is better for you sell your phone instead here on the market.
Fairphone 3 max. 80€
Fairphone 3+ max. 85€
I wonder if it is not better to sell it as spare parts since many people are looking for a bottom module
Cool idea. What parts can be sold where exactly?
I don‘t think it’s a cool idea to sell parts of a completely working phone. Try to offer the whole phone on the market place here in the forum: