Speaking from experience (failed developer here), it's a crap ton of work. It seems easy enough from the outside, but once you start the renders, it can be discouraging. For every good render you see, there may have been several attempts that sucked; hands clipping, clothes not fitting, feet buried in the floor, lighting issues, etc. Rendering 1 scene can take forever, even with a top of the line graphics card. Just rendering 100 images could take days and if you only have the one PC that can be a problem. The Dev from BaDIK has at least one PC that is only running renders. To get a release out in a couple of months is basically a full time job and most devs are doing it after work/school.
Then there is the writing and the coding, music, sound graphics... it is really tough for one person to work on. Even with solid help from people like
Orangepocalypse it's still tough.