Been using the same bike shop for the last 8 years.
I now get a standard 15pc discount on anything, and a larger discount on new bikes. For instance, i bought a brand new road bike, £45 cheaper than a 2nd hand one that sold on ebay on the same day, in the same size. I never ask for discount, just get it.
They can always (Well, 90pc of the time) beat internets prices, and will often do work for free. I’ve also got use of their workshop if needed which is nice.