The states in the middle of the country and parts of the South have lower dental prices in general. Overhead is lower in those states.
Dental implant prices vary more by practitioner than by state. Part of the reason is that some use proprietary brands that have a high cost to purchase and a high cost of education to use them. In my opinion this high cost is usually justified by results.
And some just charge more.
Because of the number of appointments and the time spread it wouldn't pay the average person to travel far to save a little.