There's a big difference between buying a frame and buying a complete nut-and-bolt kit. Most kit car suppliers will package a frame, a few body parts and the suspension bits, tell you what cars to look for in the junkyard and wish you luck. CMC fell in this category and I believe Stalker does as well. You'll find these kits tend to be at the expensive end of Locost. Of course, the amount of stuff included in the "kit" might be as little as a spare frame that someone welded up in their garage.
Then there's the complete kit. Caterham and Westfield operate in this area. You get all the rivets, zipties, nuts, bolts, hoses, etc, etc, etc that you need to complete the build. At least, that's the theory
You also get an instruction manual. In the case of both Caterham and Westfield, you don't even need to paint the car - which is a bigger savings than you might think. You'll pay more for the kit, but you may not pay more to get the car on the road in the long term depending on your problem solving skills.
I'm not saying one is better than the other, but you do need to be clear on what's included if you're looking to get into this.
With a modern engine that uses fuel injection and/or distributorless ignition, wiring can be quite a job. I've done it both ways, wiring from scratch and adapting a harness from a donor car, and it's looong.