Doing it 'trad', a sash with 16 panes in it is going to take at least 8 times longer than a sash with only 1 pane.
Done WFP - I'm only guessing (see below)
If I was doing them 'trad' I'd charge 8 times my NORMAL 'trad' rate.
If I was going to WFP them, I'd charge 4 times my NORMAL 'trad' rate.
I've only ever priced one as above - but I got the job (using WFP)
(Also - see post "what would you quote" by daniel b)
Mike