Right now Porkbun has the cheapest first year at $2.57, and Epik the cheapest renewal at $20.43. Over three years the lowest total at one registrar is $44.79 at Porkbun.
Why does .blog cost more after the first year?
Many registrars sell the first year below cost and recover it at renewal: at Porkbun, .blog renews at $21.11 after a $2.57 first year. Compare the renewal and 3-year columns before you buy.