T-Mobile stores do get commission off of phone sales. All cellular store employees that work for corporate in my area make commission off of each phone sale they do. That doesn't mean that a corporate store won't be able to price match since the manager can in some instances do a price override but that depends on the manager, their sales quota for the month, etc....... It varies by the location.
Customer care doesn't get commission for phone sales which is why they can almost always price match to the web.
Zo.