Just comparing the biggest MLB deals from a net present value perspective (what is the total contract's value in today's dollars), Shohei's deal, while still the largest seems underwhelming to me considering that he's this unicorn 2-way player. If we use a 5% rate (since that seems to be the rate MLB uses) then:
Shohei $700m NPV: $337,795,798
Trout's $426.5m NPV: 311,165,580
Betts $380m NPV: 260,163,382
Judge $360m NPV: 284,312,867
So $338m NPV is still the largest, but it's not
that much of an increase over Trout's deal from 4 years ago.
Jaylen Brown's NPV on his contract (
Spotrac reports it's actually $288m, not $304m) is $245m (calculating it when the contract starts, not when signed), which is half the length as well as half the games each year, and he'll likely be able to sign another one after this. If we were to add up the value of all contracts signed in a players 10 year prime, Jaylen's would probably come out on top.
That's all high level, on a deeper level, wonder what some of the intricacies are? I don't think the jock or state taxes apply on deferred money, so in 2040, Ohtani won't have to pay CA tax on that $68m if he's moved back to Japan (or to a no income tax state). That's just an educated guess though, tax is complicated.