95 quid is a lot, given that one delivery costs you at most 5 quid, and usually you can avoid that by having your order be over 35 quid or over 10 quid of books

95 quid is a lot, given that one delivery costs you at most 5 quid, and usually you can avoid that by having your order be over 35 quid or over 10 quid of books to qualify for free standard delivery. So there's quite a wide range of Amazon use where Prime is more expensive than pay-for-delivery-as-you-go, and I think a lot of people will fall into that category rather than the other two options of "such a frequent user that Prime is worthwhile" and "doesn't use the site at all".