Well it is, because it determines how much players ask for. If they're only made one offer and there are no offers from elsewhere they aren't going to turn their nose up at it.
The place where players are most likely to be overpaid is at the talent levels where they stand out with good-but-inconsistent form, and therefore where there is some demand. Players like Mortimer, Loko, Sandow, Lussick and Hopoate.
They don't walk in anywhere until they're made an offer. This is why the highest demand players get all the money and everyone else gets peanuts.
Lussick and Harrison were playing regular footy for the defending premiers, so of course there was demand for those two. Ryan was playing reserve grade, so he wouldn't have been on much more than minimum salary.
Do you think Beavis f**ked us on the Hayne re-signings?
The only players who hurt you cap wise are those in the top 25 who shouldn't be, and those earning a couple hundred grand more than they're worth. The rest come out in the wash. Counterintuitively, Kieran Foran is more likely to hurt our cap than is Ryan Morgan.
As for Tighe and Reddy, why would you want centres not good enough for the NRL to fill your third (and potentially second) centre slot?