Putting together my own computer and comparing the prices of the ADK and RAIN PC's I really don't see that they are over priced. Actually, the RAIN PC came in about $500 under the price of the PC I spec'ed out on Amazon.
I have bought pre assembled computers and built my own. I have horror and success stories on both sides.
I built my first computer in the late 70's from a kit. It malfunctioned when done, I troubleshot and fixed it.
I
would never buy a Persario because I thought they were
junk. I bought a Sony, in the 16 weeks that I was it's owner, I had it in my possession for about 3 weeks, the rest of the time it was in the shop. Under the Best Buy Extended Warranty I was allowed to turn it in for a replacement. The salesmen recommended a Compaq Persario. The specs match what wanted. I bought the Persario. It was been bounced around in a semi-truck for a couple of years, survived several moves, one take apart to clean the fans, and is still working the same way the day I bought it.
I had a customer that had a computer that would crash once a day. Again, it would never fail any diagnostic test. It crashed at different times, with different programs. I had one of my tech's swap her RAM with a new computer. We were buying the same computer by a dozen a month, why was hers crashing all the time. I decided to move her hard disk to another new computer. As I was pulling the hard disk out I noticed that the RAM stick pairs on the new computer were slightly different. I looked at her old computer and the RAM sticks looked the same, I pulled the sticks and found they were two different pairs, CAS was different. I got four identical sticks and put them into her computer. It never crashed again.
I built a computer that would throw a blue screen once a week. I could never keep it working for more than a week at a time. I ran the moving bit test and it passed every time. I ran every test in my diagnostic tool kit, it would never fail. We gave it away and replaced it with a Dell. The Dell has performed flawlessly for several years. The person that received the computer I built, scraped it for parts and every computer that received a part has never had a problem. Go figure!
I've built several computers since, all are still working or retired (in the closet collecting dust).
While the computers from ADK and RAIN *may* be a little more expensive, there seems to be a piece of mind to have something that I can take out of the box, plug it in and just turn it on.
When I call Tech Support I want someone that is technical, not someone readying from a script with a 2 second delay.
So to answer the OP question. Yes and no. Spec out what you want. Check it against the RAIN and ADK Machines. Spec out a PC with similar specs from the RAIN and ADK PC's. Is there really that much of a price difference? I was surprised that the RAIN came in under my price.
-JJ