carlos_mx has the right approach — we did the same thing. Converted 3 out of 8 presses and kept the rest mechanical. Three years in, here are the actual numbers.
The servo presses run our AHSS and aluminum work. Scrap rate went from 3.2% to 0.8% on those jobs. That alone paid for one press in 14 months. The energy savings are real but smaller than the brochures claim — we measured about 35% reduction vs the equivalent mechanical press, not the 50-60% that gets thrown around.
Where the ROI surprised us was die life. Our progressive dies for a stainless bracket went from 180k hits to 310k hits because we could slow down through the cutting zone. That is $22k in die costs per year on one part number.
But here is what I would tell management: do not convert your simple blanking lines. A mechanical press blanking mild steel at 80 SPM does not need servo. The servo press would run that job at maybe 65 SPM because of the motion profile overhead. You would spend $400k to go slower on easy work.
The business case is strongest when you have: (1) mixed materials on the same press requiring different speed profiles, (2) quality problems from impact speed, (3) complex forming where dwell or reverse motion helps, or (4) you are quoting new work that specifically requires servo capability. If none of those apply, keep your mechanicals and spend the money on tooling.