a calibrated monitor to your device will cut down waste alot if matching colour. use a cheap crappy monitor that does not resemble what the printer outputs from calibration - you may as well hit the lucky dip button when printing.
Overs for finishing - 10 to 20 for folding. 6-7 for cutting. Anymore required means someone doesnt know what they are doing in simple finishing steps - thats of course unless something goes wrong with the machine - that case the job gets sent back for print and matched using the job sheets.
Some factors to think about:
Mono vs. 4-Color
Book printing vs. single original
House stock vs. special order
Full Bleed vs Non Bleed
Also how many finishing steps. A +cover booklet requires us to print the cover, run the cover through our creaser, print the body while inserting the cover and if we don't use inline booklet maker using our offline. So we have more places that prints can be lost as opposed to a simple cut and drop in a box or fold. Also tri-fold vs bi-fold.
It is so hard to say especially when you start adding in jams etc. It really would depend on your shop. With that being said 0-10 sheets is our norm and longer runs can be up to 10% depending on the above factors.