I don't think it's safe to assume that paying for that service being done by someone maintaining 1000+ machines is necessarily going to be more expensive than paying to do it in-house for 10 or 100. It's generally going to be significantly more cost-efficient on a per-machine basis to have someone administrating 1000 machines vs. 100. If nothing else, the cost of specifying and purchasing hardware and getting staff up to speed on it is going to be spread much more efficiently, as is the cost of 24x7 oversight and backup hardware. Not to mention they're probably buying all that hardware significantly cheaper.