Buyer pays: $3.99
FBA per unit fulfillment fee: -$1.00
FBA weight based fee: -$0.46
Fixed closing fee: -$0.99
Variable closing fee: -$1.35
Change to your seller account balance: -$0.415 separate fees on a single transaction? This makes eBay look straightforward.
My bad, I should have done my research, but until now I've had all positive vibes from Amazon.
The takeaway is: if you're going to use FBA, which right now, I obviously do NOT recommend, you better jack your prices up.