At this point, most of the free up space is picked up by the big boys and you gotta do business with them.
Airn has a few senarios where you can pick up ipv4 addresses but it's pretty though at this point and you usually would need to be an established business with an existing ipv4 and a dual stack ipv6 setup. The ipv4 they are giving out is basically preferred to providers that are dual stacking and need additional ipv4 space to roll out ipv6.
Honestly, if you were to start today, there's basically no chance unless you gett off your wallet and pay a 3rd party at auction. And those ups are usually going to be trash. You'll spend a year getting them off blacklists and able to function.
So theoretically, you could get some but in practice, you're best bet is to rent them from Someone that already has them and put a router or server in their Colo.
An asn is not something you buy from a third party unless acquiring a whole corporation that already has one, since there is no real shortage of them, you'd get your asn from your regional registry.
Expect about $50 to 55 per IP now.
So 254 * 50 or about USD 12k to 13k? That’s the only cost and you get to own 254 IP addresses? Are there ongoing costs?