Hmmm, a £150k salary seems much harder thing to achieve than a £750 day rate, I can see quite a few DevOps contract jobs at £750 / day but no permanent ones at £150k! As you say though, it depends on how you look at it..
These usually don't reflect that skilled IT is vastly different from desktop jocky, and that it's a well paid field, thus they're forced to use contractors or outsource.
Skill wise, they're probably same same.