Your ISP probably hasn't tried to acquire IPv4 addresses recently. https://ipv4.global/reports/ https://ipv4.global/reports/ shows prices around $40/address, s

Your ISP probably hasn't tried to acquire IPv4 addresses recently. https://ipv4.global/reports/ https://ipv4.global/reports/ shows prices around $40/address, so it would take 2-3 years to break even at $1.30/month. (Although, people rent apartments with break-even periods well beyond 10 years, so maybe 2-3 is still fine.)