roboedar,
We use ASP-One (
Exchange Hosting Features and Pricing from ASP-One) for our shared Exchange 2003 plan. We have 5 userIDs, 2 with BB service. It is $10 per ID, with 500Mb storage per ID (you can pool the storage). Throw in advanced spam filtering for each ID (a few dollars) and $10 per ID for the use of a BES, which syncs very well with the Exchange server. Total monthly cost for our company: less than $80. I can't even imagine how quickly I can make this $80 back by making one client happy for a quickly returned email...