This is a good question VirtualT- one I have posed myself when talking about LLL, so I guess the same replies apply to NNN too. I think it completely depends on the buyer- if you have a motivated end-user who is looking to capture that number as their own brand, having the set can mean you can demand a far higher price, although to a reseller it may be of little consequence. Unfortunately, I don't believe there is much of a "rule" for what amount a collection bumps the overall price of individual names