There would only be 22% of their salaries left to pay this season after the deadline so your numbers are a bit off.
- Rinne 20/21: $4m x 22% = $0.88m
- Jarnkrok 20/21: $2.2m x 22% = $484k
- Jarnkrok 21/22: $2.2m
That's a totla of
$3.564m due to those two players. If Nashville retains 50% on both contracts they are only on the hook for
$1.782m,
$682k this season and
$1.1m next season.
- Compher 20/21: $2.6m x 22% = $572k
- Compher 21/22: $4.5m
- Compher 22/23: $3.5m
So this year Nashville would save $110k in salary ($682k - $572k).
Next season they would have $5.5m in cost, and the season after $3.5m. So they'd be adding $8.890m in salary ($5.5m + $3.5m - $110k) over 2.22 seasons. That's not all sunk cost though obviously, as they'd be getting value from Compher on their team, along with whatever the pick/prospect Colorado would add.
That said, if you want to make it less costly for Nashville just remove the retention on Jarnkrok, that's fine too. That knocks off $1.342m ($1.1m + $242k), so Nashville would have Compher for 2 years + a pick/prospect for a cost of $7.548m over 2.2 seasons (which is basically
$3.43 average salary per year, which is slightly lower than his $3.5m caphit).
That might not seem like the deal of the century, but recall that the value of the pick/prospect to be added is up for debate, so feel free to suggest something you think would offset the added salary.