Fixed variable cost analysis is crucial. 15k is very high. If you put 10 skilled workers on it for a year, plus development labs, it would cost about $1.2 million, including outsourcing to specialist engineers to refine the CAD files.

At high volumes, like 4000 units, that is divided to $300 RnD per unit. Obviously, it would benefit from a 2-3 million dev budget though.

The bill of materials is 3000, The metal welding is $500 and the assembly is another 500, so an open source kit would be less than 4000 dollars, and a fully built kit would also be 5000.

Husqvarna and roomba companies sell by market price, not the production price, so they can markup a high value, and they use custom circuit boards, custom plastic moulds including big thermoplastic pieces.