Responsibility to support market prices? That sure sounds like 'collusion' or 'price fixing' to me.
Let me make a suggestion ... in the spirit of friendly co-operation, why don't you link to a catalog of all your prices, so we can all see what the 'correct' prices are?
As for pricing a 'service change:' Just what is a 'service change?' Even in these forums are folks who refer to them as 'panel swaps,' and do little more. Even customers are confused, as the box stores sell 'complete kits' that contain only the panel and a handful of breakers. If the customer is confuced, maybe your quote wasn't specific enough.
Mike Holmes, of "Holmes on Homes" fame, has put out his book. Designed to help the consumer find a good contractor, in "Make it Right" he expands on his views. Some of them focus on what the bid should contain.
It is his opinion that the bid should be extremely detailed, explaining exactly what you will do and exactly what materials you will use. Then, of course, there's a complete price.
For a service change, I suspect that his bid would detail getting the permit, installing a ground rod, running the GEC, installing the panel, replacing the mast and service wires, patching the roof, disposing of the trash, and being there for the inspection. This is far different from the usual "Service change $1200" bid many offer.
Without that detail, how can the customer do anything but compare on price alone?