How much should I charge for a set up???

I have a question. If a medical marijuana shop asked you to build them a clone display and maintenance set up...not a grow room or anything fancy...just a nice set up to water, light and maintain clones for sale, how much would you ask for? My plan is a mini-hydroponic set up with a resevoir (plastic storage bin with holes and a cheap pump) set up on a timer to water the rockwool three times a day, a "MacGuevered" CO2 generator, and some simple 2500 Lumen florescents hanging over a modified, bargain store writing desk. The good thing is that I actually am an artist in my "Other Life", so I can take the Sandford and Son-esque crap and put some design to it, making it a nice addition to their shop. I figure, with some shelving, tubing, and silocone glue, I can pull it in for about $80 to $100, depending on how much I can score at the dollar store, vs. what I have to surrender to the co****cking MO**** F**ckers at Home Depot.
Ahem...excuse me. Bad experience...

My question is..."how much should I charge?" Keep in mind that the temptation to eventually work in the legal marijuana trade is very tempting, and I really do like the good folks at this co-op, but I still need to eat and all. I'd like this to lead to more work, but I also don't want to come off as a target for cheap labor.

If you were to make a "Tupperware-fabulous" Hydro set-up that would take you about a day or so to build, depending on how well the glue took, what would you charge? I'm bad at asking for a fair wage, and knowing me, I'd agree to be paid in pot...I just want to know how many grams...I mean dollars...to ask for.
Any advice?

the rule of thumb in construction is 3times the price for material,so try going with that and see if that sound s reasonable to u,and only a days work,shit ,cant go wrong there...

Thanks Rascalone,
Good advice. Like I said, there is a suck up factor that I don't want to give up...if they know of my dream of being a pot farmer, they might try to take advantage...Although, having all the pot I could smoke, I probably wouldn't notice.

As a contractor no less than doubble marked-up matterials and no more than 4x marked-up matterials.