I find that the more reasonable charges, and I don't mean cheap just realistic given the many views expressed above, come from shops where the workshop provides a large chunk of the turnover. They know exactly what they need to charge in terms of labour rates and new bikes/parts/accessory sales are run as a separate entity to keep track of profitability.
I find these places are normally 'in the middle' price-wise but generally very reliable and also have the tools and expertise for the odd job out of the norm - for example I got mudguard eyes brazed on to a frame, some other braze ons removed and a totally stuck bottom bracket removed for the grand sum of £30.