"If shooting in 4K will cost you more money and slow down your post-pipeline, and then end up in front of an audience who wouldn't be able to tell the difference, does it really make sense?"
Did you video shoot in 4k, with a rebel t3i? Or did i miss something?
Say you did with some other devices, that's probably because your audience/clientele know the difference and i'm sure you must've reflected their preference in your charges.

The Titanic.