Make that 8 seconds per signature and they'll be working on it for 16 hours or 2 full working days. At $1.3 million per day I find that reasonable.

I think you're over-estimating the time required. I've signed 1,000 art prints in less than an hour. You just need a system.

1000 prints in an hour is about 3.5 seconds per signature, not too far off my mark, and I imagine you'd need to take more fatigue breaks if you had to sign seven times as many prints.