Prices of the devices are set by the manufacturers not MTS. Normal billing on a 24 month contract with voice and data (Internet) recovers about $20 towards the device every month, similar to the discount you received up front.
If you do not want to pay for Internet every month you can pay the full cost of the device upfront and then use it on a voice-only plan.
When you own the phone, your cost from Bell, MTS or whomever is for the services you choose. Much less than you think. I Was even able to Root this phone and add 32 GB of extra ram.