It doesn't necessarily mean that drop shipping would lead to a reduced margin, it makes no difference to my suppliers if I buy 1 item and have them send it straight to my customer or 20 items up front, the discounts are the same, the only difference is reduced carriage for more items.
Depends on the market really - you sell a few (I don't mean that negatively, just comparing business models) big expensive things, he is presumably going to be selling a lot of small cheap things. Your supplier will presumably happily ship a £2000 product anywhere you want. His might be less likely to want to send 2000 £1 products to 2000 different addresses..