What audio effects there were in Sgt. Pepper’s were generated in analogue effects pedals and synths. Today, those same effects are expected to be simulated, in parallel, in realtime, on the DAW you’re producing the track on. (And modern music genres use way more effect layers. Modern pop music is a fifty-deep effects tree with one-second-long samples at the bottom, with full-fidelity rendering of such monitored in real-time as performers feed vocals and other live input in.)

Estimates are > 700 hours for the album; 700/13 = more than 50 hours per track. A lot of that time was bouncing down 4 tracks to smaller numbers for future takes.