We still get a lot of traffic and sales thru our solo girl sites, but since they are part of the TeenFlood network I think that is why they sell.
If you have a girl that is doing cam's and is really active on the site you might do ok, but you would be better off in some sort of a network where the surfer get's more than just the one girl, unless she is drop dead gorgeous of course
If your looking at a solo girl site as a money maker for you ? Might not be the best option since a majority of the models won't do it for more than a year or two anyway
So it really depends on the model, and what your expecting to get out of it!