Like I said there's only so far you can go. Just because the prices seem the same doesn't mean they are price fixing. You forget SMS/MMS is old technology and over time it's more expensive over time to maintain. A part that may have coated them $1,000 may cost them $10,000 today.
There are so many factors that dictate prices. One a good note Verizon is trying to standardize IMS worldwide which would reduce costs for SMS/MMS and will use data channels over voice channels(which data channels are more up to date).