Many would oppose the idea, but if any service (e.g. eBay, LinkedIn, Facebook) were to dump the snapshot to S3 every month, that could be a solution. You can't prevent scraping anyway.
Our S3 bucket is thankfully supported by the AWS Open Data Sponsorship Program.
(Not sure if created by the admins or a 3rd party, but done once for many is better than overlapping individual efforts).