KVAR is top notch. Kits can be found a little cheaper here and there, but KVAR won't do you wrong.
I don't have direct experience in building one, but I believe you can use a 47 receiver to build a 74. There may be some mods necessary, and if so I am sure someone will speak up shortly.
As far as to why it costs 200+ to have ORF, In Range, etc. build one...Well, it is similar to why you pay a mechanic 45+ an hour to work on your car. They have the experience, the tools, and (usually) they back their work up. Buying the necessary tools alone will get you close to 200 without factoring labor. Yes, I know many of you have built without investing that much yourselves, but I would think you would agree that if you didn't invest in the tools, you at least had enough mechanical know how to get by without...