Bergeron isn't the ideal comparable. His cap hit is 6M not 10M and it expires this year, not 3 years from now. Is a 37 year old Kopitar going to be good for 70-80 points (If he even is now, since he hasn't scored at that rate for 4 years)?
Don't hear me hating on him, he's still an excellent player. But I think it's pretty unlikely he's a PPG player again at this point. I'm not even defending the proposed trade, just doubt he scores 210-240 points over the next 3 seasons. LA already got the value relative to the cap hit out of him. This is the bad, back half of the contract.