he's trying to disprove me (showing sub 100 EUR 1200 accelerators) but he can't

those sub 100EUR are junk with limited ram expansion capability. nobody will give you his nice MKIV for less than 100 EUR at this time I assure you. Also it is not given that ebay prices are higher than amibay prices. It really depends on how the listing is made and how people are looking for that device at that time.