.email TLD is around $25/year, which seems too expensive when .com is less than a half, but it would make it easier to explain why there is no website behind my domain (as I just want something for email).
But there’s also more expensive options, so I am curious what you’re paying.
Whatever domain shows up as cheapest register on tld-list if it’s a short time use domain, cheapest renewal if it’s a domain I’m planning to keep long term.
Also a tip for people with university e-mail; you can apply to Github Education pack to get some free domain registrations alongside other cool offers.