While there's some general inflation, those turned out to be cruddy deals and there's been some revision in the market for 1st since then. The Cabrera deal was signed in 2014. Other than that, there's the Chris Davis albatross recently at $23MM, and every other one of the top 8 contracts for 1B were signed in 2012 or earlier. The last nice long term contract for a 1B was Freddie Freeman's at < $17MM AAV for 8 years, although that one may have had a discount buying out some arb years. Really, if you want to see ugly, look at the top 25 1B contracts by AAV.
https://legacy.baseballprospectus.com/compensation/cots/league-info/highest-paid-players/
I think the past few years have shown you can get 20+ HR production from a bunch of lower tier 1B FAs and just go year-to-year without the massive locked in AAV for a decade.
Harper is far younger.
There is nothing Harper does defensively that justifies a massive contract. Nothing. His bat and baserunning gets him the money. It doesnt matter where he plays. If hes worth 30+ million in RF, hes worth the same at 1B.