Although the prices are a little steep on a few items, Logic Supply generally has amazingly fair prices. Plus, the parts they sell are rare, so to make any money at all, they really need to have slightly higher prices. It's just like a grocery store in the way that you pay for convenience. I've gotten all the parts for a NES-PC and a PS2-PC (except for RAM and a HDD) for around $500 from Logic Supply. That's two solid computers, for five hundred dollars. Such a good deal!
In terms of service and quality of products, Logic supply amazed me with better customer support and faster shipping than online computer suppliers like Newegg.com. Or if you compare it to sites that have somewhat the same selection, like Mini-Box.com (Although I must admit Logic Supply has a better selection than Mini-Box), the difference in support is even more apparent.
The bottom line is that for case modding projects, Logic supply is the place to go.