I think this example highlights exactly why this doesn't happen more often and why the Oilers seem somewhat unprepared for the fact that it did.
To get a team that is as hard up to the cap as you can get to even think about walking away they had to give a player a contract at 300% of his projected value. Teams willingly take this risk all the time because who in their right mind would ever do that?
I think over the last 4 years you didn't see much of it because no one had much extra cap space. You will rarely see it with true High end players as you can't overpay enough in dollars or term without coming up against the 4 1st round picks. Mtl tried with Aho but were unwilling to get into the 4 1st rounder compensation so all they could do was attack Carolina's perceived lack of cashflow by front loading/bonus loading as much as possible. Carolina had the cap space to match, Mtl was hoping they didn't have the cash flow to match the structure.
Where a offersheet makes sense and is relatively low risk is exactly in a scenario like this one. Signing him to 300% seems like a lot but it isn't. Its about 6M spread out over 2 years to get your hands on a former high 1st rounder who looks ready to break out. In the Sean Monahan trade (Cal to Mtl) if we go back to when it happened when most though Monahan was done, Mtl essentially paid 6.75M in real cash and a 1 yr cap hit to get a late 1st round pick. I think Broberg has more value than a late 1st. So the Blues are paying a 2nd (compensation) and 6M over 2 yrs for Broberg who i think we can agree is worth more than a late 1st (Edm would not have traded him 4 a late 1st at this years draft)?
Why does it not happen more often, you need a team willing to do it like St Louis with some extra cap space and you need a team that puts themselves in a vulnerable situation by spending most if not all their cap space on the UFA market and does not save enough to sign their RFAs who are eligible for an offer sheet. Especially when its more than one guy then you open yourself up to the 2 offer sheet attack st louis used
Ottawa put themselves in the same situation with Pinto last year after they signed Tarasenko. I expected one then that would have been structured to make it hard for sens to match. The Broberg type contract at the max of the 2nd round compensation would have done it as ottawa would have needed multiple subtractions to become compliant. Sens may have got lucky with his Gambling issue scaring would be offer sheets off.
From the side of a team who is willing to do it, needs to be a team with lots of real money and cap space. Most of the big $$ teams are usually close to the cap but what about when they are rebuilding? why don't teams like Mtl and Chicago why have the dollars do it now while rebuilding? probably worried about the revenge offer sheet. a rebuilding team will have lots of promising RFAs coming and some they will try to walk the line with on short term low value deals until they know what they have- can't give everyone 8X 8M after 2 years into ELC.
At the end of the day this happened because Oilers put themselves in a vulnerable spot. Had they left a little flexibility St louis would not have tried as its not in their interest to piss off a rival GM without a legit chance to get the player.