Yeah, ARIN is $500/yr for ISPs using a /22 or smaller of IPv4 space (i.e. 1022 addresses), $1000 for up to a /20 (4094 addresses): https://www.arin.net/fees/fee_schedule.html

RIPE is a lot pricier for small members because it isn't tiered. Everyone pays €3800 the first year and then €1800/year thereafter: http://www.ripe.net/lir-services/member-support/become-a-mem...