There is a requirement to be able to set different pricing for FBA Listing and Merchant Fulfiled listing on Amazon.
All FBA listing require to ge FREE postage, where as merchant fulfiled have postage seperate. Therefore the retail price for each are different.
SKU1 = £19.99 + £3.99 postage (Merchant Fulfiled)
SKU1 = £23.98 + Free postage (Amazon FBA)