I just dont understand the reasoning for having staff salaries go up so high.
It's a mechanism that forces you to give this part of the game at least some thought.
This system actually is more forgiving than the old one, where you had to check your staff every week to make sure you see if someone drops their skill. And then hope there's decent staff to replace your staff member. Now you only need to worry about the finances in the long run and that's pretty easy to plan apart from the bidding system, which may take some more work/time.
As you pointed out in somewhat different words, simply going out and buying some guy makes no sense. You need to figure out the expected benefit you get from your staff and the overall cost (which includes the "signing bonus" and the wage difference to your current staff member).
I think the new system is pretty nice. The weekly raise thing is weird in comparison to real life, but it has a sensible explanation from the game point of view. You need to make longer-term plans, but there is no similar weekly micro management feeling that the old system had. I didn't like that.
You can also just forget about the staff system and go with level 1 guys. I believe the difference to higher level staff is surprisingly small, although I don't recommend that choice for anyone.