I think this type of bolt is expensive because of the way they're tempered after manufacture. They are designed to stretch till they reach the correct torque at which point they aren't redo-able. I guess the structure of the steel changes at the elastic limit.
Having said that, I'm pretty sure that not all such bolts (there are lots around the car) are renewed, even by the MGR depots (as was). However, I bet most places renew the head bolts for example. Why should the camshaft sprocket bolts be regarded different? I dunno? The front seat anchor bolts for example were not replaced at my local Rover dealer 'cos I asked them, even tho' the manual says they should. Whether ones on the engine are regarded different I can't say. I guess you have to take an informed decision as to the risk. It's a big expensive job anyway.
