Ideally you shouldn't require users to make an account to make a purchase at all. There should be a "guest" path for purchases. Some sites still get this right. I can buy anything from plane tickets to pizzas without having an account on the company's website. Meanwhile half the "Show HN" non-commercial toy websites I come across seem to require a confirmed email for no good reason at all (probably because the webdev is hoping his little toy website somehow becomes a real business, and then he can spam my inbox with updates about this and turn me into a paying customer.)
Off the top of my head, here are some companies that don't require me to confirm my email address when making a purchase or an account: Southwest Airlines. Dominos Pizza, Hacker News, Reddit.
If those guys don't need a confirmed email address, probably your site doesn't either.