@PigFish just an idea...create a gofundme page so people here place a nominal amount for the development of this project. Obviously the amount would provide the person an opportunity to buy the KIT at a discount. There is definitely an interest from people as wineadoors seem to be a fairly popular route for many BOTL.
I can appreciate R&D costs and if you can raise the required funds through crowd sourcing to lessen the "sting" and you end up making a marketable product then it might be worth it doing it that way.
But to answer the question of cost a breakdown then (AUD$):
Wine cooler = $180 to $450 depending of brand
Passive humidification =$70 plus shipping from USA($30)
Active humidification = $200 for a cigar oasis
Hygrometers = $10 each
Data logger = from $50 to $1000.
this is not counting cedar trays, etc
So on average the cost of this build would be around $580 AUD.
Just my 5 cents