the museum has the originals of pre 1900 (approx) wills - transferred from the old Rolls office - they are however not brought out (some are very fragile) unless the microfilm is unreadable. The major cost is finding the will on the microfilm as only Archideaconal wills were numbered prior to filming - the films of the episcopal wills to 1800 have been re-indexed (and given frame numbers but these are not on the film thus serve only as an indication of approx position) by volunteers (there are many that are not in Brian's index + several that were originally wrongly indexed) - my own estimate is about 10mins to find an Archideaconal will + nearer twice that for an episcopal (assuming motorised reader) then allow 10-15mins minimum for copying as the museum does not operate user-controlled copiers.
The handwriting on wills seems to deteriorate post 1800 (and the filming is not that good) and the wills get longer (and the % of burials is reduced)
The museum microfilms are effectively those produced by the mormons but some are of an earlier vintage than those currently distributed and the splicing is different thus creating some difficulties when using Brian's index. I suspect that Brian did not check the description of each film as his indicated film number is not always accurate when a year overlaps two films.