You get what you pay for...yes...but sometimes you get good value too, even at the mid-range of the market. I can't afford to have my car serviced by the main dealer, it is too old to warrant that "premium service". My mechanic comes to the house (20 miles), drops off his courtesy car and takes mine away, and brings it back when he is satisfied that all is good...and he charges £60/hour labour. I'm happy with that, it suits me, and he is a good mechanic.
Paying cash is always a game, and too few people see the catch...
I had a plumber fit a shower pump for me...not a difficult job, but a time-consuming one and it was needed in a hurry and I simply hadn't the time to do it myself. He charged me the shop price for the pump, and again £60/hour. He asked if I wanted VAT invoice etc and I said yes, because with an invoice I could set it against the rental income, and I had a comeback if it failed.
Maths: Price for the labour was £300 +VAT of £60 =£360. He said he could "lose" the VAT for cash. Thus, I save £60. He however makes £300 either way. £360 and he pays the vatman £60, so pockets £300, but minus income tax at 40%, so he nets £180. £300 cash and he makes, well...£300! No tax, no comeback. So, I save £60, he saves 3x that, I have no invoice and he has no liability. Therefore, offering to "lose the VAT" is a very poor offer for me...if he wanted cash, he would have to come down to £200...he gets £200 and I save £160...or somewhere in between.
And that is just one of many reasons why prices vary so much.
As an aside, I put in the power supply for the pump and as it's Scotland I didn't part P anyone. However, I did get a proper electrician to do my testing afterwards of that new circuit and the new supply to the smokes...and I was happy to pay him his charge for that.