As a Business we used to list items if they where not on sale at there RRP on the marketplaces and not put any price inflation on. We found that this was quite successful and helped with sales on full price items as customers go online expecting to pay the RRP. Then on all sale items we would put a price inflation on these to cover the cost of the market place. We may be loosing a small amount on full RRP items but hopefully the margin was there with the item to cover this while on sale items our margin was already cut so we needed to cover fees. 

It would be great if this could be built into a next build as in a price competitive market place selling at RRP will help sales then anything reduced you are still covered on.