first off, welcome to the forums.
What is the purpose for them wanting the model, bathtub toy , display, etc.
After you have determined where they want to put it, then you choose how much YOU will invest in it. Are you going to invest with any AM stuff ?, if so, you should include the price of that in the final price, what the prices of paints and such are and how many hours you put into it. Along of course with the kit price.
heres a link to a site that might help.
http://modelingmadness.com/reviews/misc/ships/robertoqm2.htm
and another
http://hsfeatures.com/features04/qm2tt_1.htm
figuring the price as $75, you invest in some PE stuff, that adds $10-15. Figure it takes around 150 hours of actuall build/painting time, I would charge maybe $500 for that, If I had to guess, that total wuld be around $600. Now if the co-worker were the boss, maybe throw in a little discount.
Just my input, I could be totally off though.
Regards,
David
On the bench:
1/35 Tamiya M26 Pershing-0%
1/144 Minicraft P-38J Lightning-50%
Numerous 1/35 scale figures in various stages if completion.