TT, the best analogy for youas a customer is getting some building work done.
The first thing you find is that your choice of contractrs soon becomes limited. First some put in silly bids just in case you are stupid. Eventually one puts in a sensible bid. So sensible that the contractor realised he underbid and so fails to turn up.
Then you start again, perhaps with a new spec. As your contractor starts work Mrs TT decides she want a change - underfloor heating say. Now there is little extra work for the tiler but that doesn't stop him doubling the price.
See where I am coming from?