The key in offer sheet fear-mongering is why would the player sign one? Perhaps that's the reason they aren't signed more often; the player is happy with his current team.
No reason to think Monahan wouldn't prefer to sign a long term contract with the Flames for very similar money to what any team would be able to offer.
Also here are the list of teams that have the required draft picks to make such offer sheets:
http://www.generalfanager.com/draftpicks/offersheets
Of those that have the picks for a $7,305,316 to $9,131,645 offer sheet, how many will likely have $8M in cap space for next year without doing some drastic moves?