These are players being signed from the free agent pool.
I'm definitely torn in that I don't want to stifle the creativity of my owners, so I'm inclined to do as you say and let it play out. However, these signings seem particularly improbable and potential unbalancing. The examples you listed were older players, mostly mid-30s. It's understandable that owners would shy away from signing them if their demands are ridiculously high.
The players involved here, though, are highly-rated and in their prime. Two examples: SS
Héctor Castillo and C
Jeffery Graham, both 26-year-olds signed in July for $2M/season (Castillo for 3 years, Graham for 4). Castillo, an outstanding defensive SS, posted a 38.9 VORP in his age 25 season. He had been asking for $19M/season and was still asking for an 8-digit 1-year contract when he agreed to sign for $6M over 3 years.
Graham, also an outstanding defender, posted a less impressive 18.9 VORP in his age 25 season. He them spent the first half of '08 playing in our AI-run Mexican league where he amassed a crazy 71.9 VORP (although, to be fair, the Mexican league skews heavily towards offense). He was asking for an $8M 1-year contract when he agreed to $8M over 4 years.
That's what I find really crazy about this situation: how do these players go from demanding a 1-year, $8-$12M contract at the start of a sim to settling for a multi-year deal at a fraction of that yearly salary by the sim's conclusion? That just doesn't seem logical. A number of my owners have noted this and have complained loudly. It's not helping that the beneficiary of these two examples was already far and away the best team in the league (not that they did anything wrong here; it's the game's logic I'm questioning, not their actions).