$250/month sounds like nothing at all for a site with a claimed 4M MAU. The enterprise rate of $10k/month sounds a lot more reasonable. If everything presented here is accurate, I'm not understanding the sharp discrepancy in pricing tiers. If anything they should've already been paying more than $10k/month for massive traffic on the basic plan and then be able to save money by paying for massive scale when negotiating rates for the enterprise plan.

Also this sounds like an online gambling site of questionable legality, knowingly serving customers in jurisdictions where it's illegal, so I can't say I have too much sympathy, and I feel like Cloudflare effectively fired them as a customer when they realized what they were up to.