Today I had to make a detour to the bike shop as a jockey wheel decided to fly out of a friend's derailleur. The shop were able to supply a replacement retaining bolt free of charge, however the only jockey wheels that they stocked were cartridge bearing ones at £20 a go. Needing to get home, the derailleur received an unexpected upgrade.
I did not notice any speed improvement on the way back, the jockey wheels didn't strike me as being featherlight and the shifting worked the same as before. I was beginning to wonder 'if we had been had'.
So, what is the point of expensive jockey wheels? I can see the benefit for the shop, but not for the cyclist.