I'm assuming everyone on this site has put a computer or two together and myself I've done between 30-50 as a desktop support agent at a large corporation. But after I moved on I still continue making them for myself...if you think putting it together physically AND installing the OS and updates/AVG takes only a 'few' hours you're crazy. They wouldn't be making great margins. A company like this wants to be charging you $100/hr...not $100/3hours. That's not how you run a company. Thing about iBuyPower is it's not people like us that buy them...it's the people that aren't comfortable building them or don't know how but can afford to add $200-300 to the cost of the system to have it build and shipped. I wouldn't do it, but I get it.What they should offer is a service where they charge you $100 to assemble a computer for you, install the OS, AVG Free edition and drivers. Then you pick any part you want from Newegg at normal prices. All the configurator will do is make sure you don't choose and incompatible parts and make sure you have all parts needed for a functioning PC. For the OS you pick Linux, FreeBSD or Windows (with a true OEM licensing fee such as a small manufacturer would pay).
At $100 they'd be making great margins. Since labor would run about an hour to an hour and a half at about $20 per hour. I know techs wouldn't make $20 per hour but you have to factor in all the mandatory employment taxes and insurances hidden from the worker that the employer has to pay.
More complex configurations such as RAID, custom cooling, additional software would be done for an additional fee.