Right now Porkbun has the cheapest first year at $3.09, and Porkbun the cheapest renewal at $10.76. Over three years the lowest total at one registrar is $24.61 at Porkbun.
Why does .onl cost more after the first year?
Many registrars sell the first year below cost and recover it at renewal: at Porkbun, .onl renews at $10.76 after a $3.09 first year. Compare the renewal and 3-year columns before you buy.