That's one, very simplistic way of looking at it. I would say in both cases it was the player and the retention that netted us the first round picks and in the case of EK, it was the player, the retention and taking back 15 million dollars in salary that got us the pick.
In terms of Vegas and Hertl, with 6 years or retention, an argument could be made that we could have accumulated far more draft capital value with that retention spot than a super late first rounder.
Again, I understand why it was done, but part of me feels Grier was a tad impatient out of fear he'd never get anything close to the value he got again.
In terms of rentals highly unlikely netting us 1sts, you're probably right, but there's also a ton of teams willing to do what Calgary did with Monahan. Imagine the idea of a team dumping a high-priced underperformer with a 2nd and a 3rd (for example). At worst that's what we get back, at best, well like I said, Hughes ended up getting two first rounders from Monahan.