Faff said..
Sorry, didn't realise they were such hard workers. Do their IPs trace to Nigeria by any chance? (Although, in these days of cheap VPN, IPs mean little).
no worries ..as you suggest,some tech makes it challenging. Plus, with pre-validated stolen credit cards, it makes it even more challenging.
They are such time wasters.

We already have some nifty systems that catch the email spammers - you'll note there is practically zero Private Message spam these days. Our systems actually occupy them for a while ... it's great to check the logs, and see that a spammer has spent 4-6 hours (seriously) manually spamming everybody, and yet not a single one got through!
These other guys are a bit more trouble though, and we're building things to catch them.