The last time I was asked to check, NetJets was somewhat cheaper on the one way legs or the "bring-me-there-and-take-me-back-2-weeks-later" trips. Any roundrobin, the usual suspects are cheaper. But I think it comes down to marketing, It is (or was?) "chic" to be a Netjetter. Buy an apartment in London and get a Netjets card for free. Buy a yacht and get a NetJets card.
Why bother owning an airplane NetJets can do that for you etcetc.
WE all know we could do all this as well, but does Joe Averagebillionaire know?
Its (relatively) new, its hip and trendy and its not identifiable either, so if you board that Jet, your miserable neighbour (or union) does not know its yours...
Definately a factor in Germany, was told so by a former client.