Here
Sorry, I don't see the word "data" anywhere in there.
Show me a plan comparable to AT&T or Verizon's that includes data similar to their's for the $40/month you quoted and I'll accept your argument. Otherwise just drop it because you have nothing.
Edit: I can't find this $40/month including basic data plan you speak of. Is it still offered?
Considering the OP, I'll accept one statement from you as being factual.
"If you are willing to accept a much slower data rate, you can purchase an unlocked iPhone at full retail and activate it on T-Mobile."