If you pay over the odds then have a reason to do so - otherwise pay the minimum.
One of those reasons to pay over the odds might be support local shops, or support a specific shop of choice.
However, for a motorbike, locality is neither here nor there, since you can normally ride to another dealer/fitter.
Another reason might be for safety (or perceived safety). I go to Wheelhouse Tyres because I trust them, and I definitely pay above the internet price (£289 fitted). However, that's my call.
If Rae has no affinity to the local tyre seller / fitter, so be it. The fitter will still make a profit from the fitting, assuming he's not cocked up his pricing.
A smart fitter might enquire what price Rae got the tyres for and see if he could match them the next time around - thus increasing his profit.
If he's not making a profit, he's likely to go out of business, and Rae will have to go elsewhere, possibly spending a bit more fuel at a higher price - but that's a market economy for you.