Did you also figure in the cost of the misc stuff --- ie. Mouse , keyboard, speakers, cables, misc wiring, thermal paste, labor cost for assembly, packaging materials, shipping insurance, credit card fees, Time loss dealing with any DOA product, Legal licenses of included software (remember most prebuilt units will include a copy of WIndows and some other programs), Warranty support you need to provide to your purchasors (if using OEM software companies like Microsoft require the builder to offer support !!) - Also shipping fees for sending you any systems covered by your warranty and replacement parts , Cost of purchasing the products before sale and pricing fluctuations during the time between purchase of those parts and the final sale (prices drop quickly and you might wind up having to sell at lower pricing than what the cost of purchase was if you hold much inventory in stock !), etc. --- once you add all of those and still include any profit margin you'll find it hard to offer pricing to match the larger prebuilt companies and my find it hard to convince users of the benefits of buying from you. ---- Better to offer assistance in speccing and building systems to order for a fee and help in finding the parts for the best prices rather than have to purchase and hold inventory of items that are dropping in price.