A quick breakdown of the costs of selling 1 x 12″ record for £1 plus shipping (£4.20) via eBay:

Total Sales: £5.20

Total Costs: £4.72

Record Mailer: £0.30
Postage £3.90
Final Price Fee: £0.10
Final Value On Shipping £0.42

That leaves a whopping 48p profit for the sale of the item!?!
Postage is getting bumped to £4.80..