Give them the data, and let them deal with it. (Score 1)

If the customers are allowed to ad-hoc query the entire database, they may just as well have a copy to keep for themselves... So why not export the data (or replicate it out) and give it to them? You can be nice and offer to host their database server in your datacenter, but let them be responsible for running it. If they balk at the work of doing that, charge them to perform that service.