Just find a Hoster with low traffic egress cost, reverse proxy normal traffic to Cloudflare and reply with 2GB files for the bot, they annoy you/cost you money, make them pay.
But since AWS considers this fine, I'd absolutely take the "redirecting the entirety of the traffic to aws abuse report page" approach. If they consider it abuse - great, they can go turn it off then. The bot could behave differently but at least curl won't add a referer header or similar when it is redirected, so the obvious target would be their instance hosting the bot, not you.
Actually, I would find the biggest file I can that is hosted by Amazon itself (not another AWS customer) and redirect them to it. I bet they're hosting linux images somewhere. Besides being more annoying (and thus hopefully attention-getting) for Amazon, it should keep the bot busy for longer, reducing the amount of traffic hitting you.
If the bot doesn't eat files over a certain size, try to find something smaller or something that doesn't report the size in response to a HEAD request.
What I'd do is block the AWS AP range at the edge (unless there's something else there that needs access to your site) - you can get regularly updated JSON formatted lists around the internet, or have something match its fingerprint to send it heaps of garbage, like the zip-bombs others have suggested. It could be a recursive "you're abusing my site - go away" or what-have-you. You could also do some-kind of grey-listing, where you limit the speed to a crawl so that each connection just consumes crawler resources and gets little content. If they are tracking this, they'll see the performance issues and maybe adjust.