Again, it's a bit expensive but hey, look at the "fourth line" the Stanley Cup champs rolled out this year (Steen - Barbashev - Sundqvist) which was almost more like a third line, but regardless it's an pricey one, especially now that Sundqvist re-upped.
Avs have some leeway here at least. They can afford to bolster the bottom six with veterans because they have a number of players either already on the roster or on their way in on ELCs. One would hope with all the friggin' bodies in Loveland that one or two of those guys will pan out as a role player of some kind at the NHL level.
If the Avalanche actually succeed in icing a more balanced lineup, it might be a first. They've always been a bit top-heavy in their glory days. I can still remember when Hartley rolled out a ridiculous lineup on opening night that featured scoring line winger Steve Brule (not the Adult Swim guy, the guy who turned around and shot on goal...right at Patrick Roy) and Alex Tanguay on the third line. No one here is saying they should be more like the Blues, all they have to accomplish is icing more than one line that can score and take on some defensive matchups so that the top line isn't getting overplayed.
The analytics guys insist you should just be throwing ELC guys as your 4th line, but that's just never, ever gonna happen. And really...I'm not sure it should. At some point, as Henchy pointed out, even your in-house 4th liners will become too expensive, so you just dive back into the bargain bin to get another one. It's not that hard to get a reasonably good fringe player to eat up 10-12 minutes a night and play every shift like it's his last. There are a ton of players who want that opportunity.
The key is not the money, it's the term. That's why that contract for Brandon Tanev is so ridiculously insane (and to a lesser extent, the amount of money Garnet effin' Hathaway got from Washington). The Avs learned from handing out three-year deals to their lunch pailers a few years back, it's just not something you should do. None of the 4th line guys are signed for more than two years. Term is a bit long for 3rd liners (Compher and Donskoi) but that's gonna happen from time to time.