and at the same time you could buy a phone with a larger screen for the same price or less
t-mo started losing all their best customers after the iphone came out and charging slightly more for phones was a way to make more money from existing customers. and the 4G price for existing customers is a lot more than what AT&T charges for the Insprire
Not everyone wants a big screen. If everyone wanted a 4.3" screen, the iPhone and Droid phones wouldn't have been so successful. I had an HD2 and don't want that size again. 4" or lower for me.
Also, you are completely off on the customer base. T-Mobile has lost customers overall, but revenues are up, because their percentage of smartphone users has drastically increased.
T-Mobile absolutely does not charge more than the other carriers. You are fixated on the MT4G for some reason (falsely, I might add - your attacks on that product have been roundly shot down), but look at their entire lineup - it is right in line, if not a little cheaper than the competition. Top phones on Verizon and Sprint are consistently $250 or so, after rebate, whereas they're generally $200 or less on T-Mobile outright, plus they run the sales I mentioned earlier that the other carriers rarely do.
You obviously don't like T-Mobile. That's fine, everyone is welcome to their own opinion - but the "facts" you're trying to use to disparrage them are just flat out untrue. Come back when you're better educated on the subject.