I think it's possible to overspend on the bullpen at 80M. And that means less money for everything else.
One recent team of mine at the 80M level won 101 games with Narleski (1.85 M), an R3, and LaPalme (1.77 M), also an R3, as my two main relievers. I had a 5 man rotation. My other two pure relievers were a .56M guy and a .5 M guy.
My total bullpen expenditure was 4.68M, or just under 6% of my overall 80M budget. And the results weren't bad. Narleski pitched 182.2 innings and LaPalme pitched 93.2 innings. They combined for a 21-11 W/L and 39-22 saves. The two cheapo relievers combined for 69.1 innings, a 3-1 W/L and 3-1 saves. I got a few relief stints out of SP/RP starters.
The rest of the money on this 101 win team went into starting pitching and offense. My hitters scored 1065 runs--which they couldn't have done if I'd lavished money on a bullpen where the #3 & #4 guys pitched just a few innings. My run differential was +250.
https://365.strat-o-matic.com/team/1533409There are plenty of ways to construct a winning team--and the cost of bullpens in this particular league ranged tremendously— but in an 80M league I wouldn't spend to much on the bullpen unless I was loading up on super-relievers who I was planning to ride for 40% of my innings.
Update: I just checked the league and found it had another 101 win team. That team expended 2.32M on its bullpen, so my bullpen expenditure was profligate by comparison. Again--there simply isn't one right way to construct a team, let alone a bullpen. But it's good to have a plan for how your team is going to cover its 1,400 innings for the season.