Right now Porkbun has the cheapest first year at $1.54, and NameSilo the cheapest renewal at $11.48. Over three years the lowest total at one registrar is $24.95 at NameSilo.
Why does .monster cost more after the first year?
Many registrars sell the first year below cost and recover it at renewal: at Porkbun, .monster renews at $14.21 after a $1.54 first year. Compare the renewal and 3-year columns before you buy.