When you weight 390lbs nothing is cheap, especially bike parts. If this were a 32 spoke wheel I could go with a much cheaper hub but for a 48 spoke wheel there are no cheap hubs. Given my weight and the amount of power someone my size transfers to the rear wheel everything has to be able to withstand the abuse.
Besides, I don't drink, I don't smoke and I do pretty well and don't have any kids so this isn't a bank breaking purchase. What's $700 if it improves my QOL significantly and keeps me on the bike riding. If I'm down another 50-100 lbs by this time next year I'm going to get Powertap hubs which will easily be $1,000 in hubs only.