How did you get to that result?
That's not too hard at all. There are 3 staff sorts, with all 7 levels. So that 3/21 which is 14,3%. I said less than 15% because there are only a few lvl 5s, 6s and 7s compared to a lot lower leveled staff. So it's probably even less than 10%, or maybe even less than 5%.
Still sound like a good deal to you?
Yeah it's a great deal, and I have several reasons to say this;
1) The starting salary of the staff is way lower than in the old system (even the most expensive staff, of course the 6s and 7s weren't in the old system, so it's useless to compare), it takes at least half a season with the current weekly raise to be close to the salary of the old system, so you save money for at least half a season. I've still got my lvl 9, now lvl 5, coach from the old system, and he's still not at the wage he had when he was converted into the new system, same story for my PR.
2) In the old system you kept paying the same, while your staff might drop levels, so you paid (using your example) 25k signing fee and a higher weekly salary + skill drops vs 31k signing fee with a lower weekly salary and without skill drops.
I like it.