Model 8 and model 10 will most likely refer to cpu core type, with 8 being tbred, and 10 being barton (could be tred b not sure)
I notice if you go via cpu selection mode they all have a model listed apart from the 3000+
Looking at the cpu supported list, 8 is tbred and 10 is either barton or thorton (latter is barton with half the cache) the lower cache could explain the price difference between it and an xp3000+ As i said earlier i wouldnt trust ebuyers description to be precise.
Though i have just found this,
http://www.amdboard.com/sempron_3000.html