AAV is the only salary data needed for large market clubs.
That being said, I expect to see some interesting machinations on that end in 2019, so much so that I think the new CBA will change that. You are already seeing it with Stanton. Stanton signed the 13 yr contract at an AAV of $25 mil. So $25 mil is what is on the books, even though the Yankees took on $295 mil over the final 10 years. With the Marlins kicking in $30 mil, the Yanks AAV is only $22 mil, which is actually pretty reasonable for someone with Stanton's talent. Based on what we are paying him, it should have been $26.5 mil. From a lux tax perspective, it helps us to keep him on that deal.
I also expect teams to do what the sox did with JD Martinez. Front load a contract and offer an opt out. I expect this with Harper. I think Harper sees a contract in the 12 yr $360 mil range, but I expect him to see a much higher AAV over the first 3 seasons. Watch, he will sign a deal that is two deals in one. 3 yr $120 mil deal with an opt out followed by a 9 yr $240 mil deal if he chooses to stay. Harper will effectively see a $40 mil AAV and then opt out while having only a $30 mil AAV on the books. The back end is if he gets hurt or fades, which he shouldn't as he is so young