I concur on the price for it's market's value range...
Musicians (often) spend like a kid who got 100 bucks from granny on xmas.
Look at alot of the DIY synths out there that sell for big money - IN KITS.
Getlofi has IMHO pretty homemade stuff they sell for more than shield prices.
Not to mention the "doomsday circuit bending kit" which is an electronics goldmine find (i got 150 at 45 cents each !) they offer for 20bucks!!! Makershed did the same thing but 25% pricier: http://www.makershed.com/ProductDetails.asp?ProductCode=MKGLF1&Click=19209
They added value by supplying a printed manual. That's a good idea - I believe you mentioned that you will be doing that.
I suppose it's supposed to be "green" since all the parts are "surplus"...
Check out other prices out there - add up there costs in bulk for components and then figure their profit margin with your supply resources:
Drone labs :http://casperelectronics.com/for-sale-2/
Voice of Saturn:http://store.curiousinventor.com/voice-of-saturn-modular/voice-of-saturn-synth.html
Music from Outer Space:http://www.musicfromouterspace.com/mfosweb/navigate.action?CATPARTNO=WSGCOMPKIT&MAINTAB=CATALOG&PROJARG=RINGMODULATOROCT2007/RINGMODULATOROCT2007.html
But, arduino kit builders are used to much lower prices I think...
So there's a good note about markets.
And for no reason should you lowball the price of your product...
You don't make friends in business by giving it away... excellent quality, support, and contribution to the online community is key IMHO.
Most people perceive a higher value on higher priced items in comparison to the same item at bargain basement deals.
Heck sparkfun adds a ton of "value" to their products with only red boxes for packaging! People love the boxes and buy from them because of that. (see their forums )
And having a enclosure option is huge and very profitable...
Don't feel bad if you feel you don't want to charge too much...
There's alot to learn and heed the advice from everyone everywhere in business...
Do NOT lowball your prices, or you will learn the hard way working with no personal gain, and spending much more time than you guessed it would take.
Learn from those who've done it and succeeded... don't learn the hard way!
This is all under the school of value sales over quantity sales.
I've done quantity(not kit biz)... big mistake. Hard to change prices later.
Much better to sell a product for 3x price and work 1/3 the effort and only sell 1/3 the volume ... than it is to sell 3 times quantity and have 3x work/stock/mailing for the same amount with lower profit margin (because parts cost 3x).
Remember - it's not just making a kit/product and then it's all gravy.
Shipping alone is a total bear - PITA at smaller volume.
Ok... sorry all - rambling again... CHEERS!