While true in some instances it doesn't always hold true. There are a few things to remember.
1. Vinyl isn't all created equal. if all you are looking at is price, you could be very disappointed down the road when the print starts to fail and starts to come off the wall. If you can find a shop that is using 3m hp you may pay a little more but you'll not have the headaches down the road.
2. If you compair prices with a shop in a big city with a shop in a more rural area that will have to ship it out sometimes it is still cheaper to have it shipped because of overhead and living costs.
Where this all doesn't exist is when you find a shop that is over extended and just needs to have their machine running all the time. They will print for pennies of profit, just to keep the machine making its payment, the problem using a place like this is if there is a problem with the print is usually a struggle to get them to replace it because their margins are so low.
We ship all over the US because we are in a small town and our cost of living is lower, I also have a BFA in Art. So topically I'm pottery good seeing colors.
I'm not saying to use me just know that because you find a local shop doesn't mean your getting the best job & price. Check around.