The only "kit" I am aware of was the Rutex THC kit to build a DIY THC. By the time you bought all of the parts it was about 500.00 and it was a mechanical nightmare. It lacked a lot in features and function. Later they introduced a combo driver/thc card but it was tied to their plasma cutting software and not a lot cheaper.
I'll wax philosophical on this and say that I owned a mail order business in the early 80's that sold electronic components to electronic experimenters. We had a line of kits we developed and we sold thousands over 8 years. Bear in mind this was to persons that were (supposedly) electronically inclined (i.e. Ham Radio operators, electronics technicians, and engineers). It was in the heady days of
Popular Electronics, Radio Electronics, 73's and other publications. I was amazed at the kits we got back for repair (some with nasty letters) that looked like they were assembled by a 4 year old and soldered with a hot rock. Parts in wrong, parts in the wrong place, cold solder joints, PCB damage from too much heat, etc.
The worst reason to buy a kit is because it's cheap. If you have the technical skills to properly assemble, test and use a piece of equipment with minimal (or zero) support, and your spare time has no value, then kits make sense. If you want a learning experience then working at the component level has rewards. There used to be a company named Heathkit. They had all kinds of kits when electronics were expensive. You could even buy a 25" color TV Kit from them. Their manuals were excellent and the components were good quality. At a point where you could buy an assembled radio, TV, power supply, etc for less than a kit it spelled their demise.
I would have nightmares about offering a kit or parts where there are lethal voltages involved to non-technical builders. The problem with just a PCB is that the card is layed out for specific components. If you deviate you better know what you can substiute and what you can't. You have to source all of the parts and unless you live in an area with a really good surplus electronics store, your cost of parts in small qty and the freight to get them will quickly eat up the concept of "low cost".
Consider also that the MP3000 unit is also a full powered, isolated BreakOut Board (BOB) which is another piece you will either have to build or buy.
I understand the idea of doing things on a budget. Also understand that the "hobby" or "project' you choose will have cost factors. You can't build and fly an RC airplane for $30.00 unless you have the skills to build your own small servo receivers and circuits. You can't get into metal working (lathe, Mill, welding) for a few bucks. Woodworking can be done with relatively cheap tools but as soon as you want to do more complex projects you start to "justify" that table saw or router table you saw in the tool catalog!
TOM Caudle
www.CandCNC.com