Did you ask them what a "2 virtual web servers and 2 virtual mirrored databases"
supporting #x people running #y software would cost? A $15K 4 node system just seems high unless you have 60+ people. Database servers, Web servers and the usual IT tasks (email & office applications) just aren't all that demanding on hardware.
Of course you know more about the actual requirements, the software and the number of people you're supporting. You haven't shared that with us.
I think it's a good idea to get with the business consultants at Dell or HP and go over the requirements with them. They're the experts at matching requirements to hardware.
And let us know what they recommend.