Paul, its totally down to wear rates as to what needs replacing and this is down to type of usage. When I quote 10K miles thats assuming the car is for weekend use and trackdays only, so that most of the 10K is relatively hard miles.

At a freshen up the main areas to check for wear are bores/rings, shells, oil pump, cams/followers and valve guides. All other parts tend to be reused except for the new gaskets of course.

If the bore wear is good, then it will consist mainly of a rehone and new rings, new shells, check oil pump, new valve guides and seats recut and then rebuilt.

Hence you can see the big cost at a freshen up comes from whether the bore has worn. In this case its a rebore and new pistons which adds significant cost. Most however are ok at 10K and usually require a bore at the next 10K freshen. (i.e. 20K miles total)