We all know cheese production gave an ridiculous amount of feps for almost no effort, so it needed adjustment, which happened with domestication. The milk income has been significantly lowered, basically it has been kicked in the nuts, then thrown into a river, then shot with a pumpgun, but meh.
However, the downside of this, is that carrotcakes, applepies and raisincakes are redundant items. No one would waste precious milk for such low fep items when they can have cheese. Furthermore Psy gain got shot too. Its now even easier to get bulbs than the needed butter, and yes it was a pita to gain bulbs!
So i think it wouldn't hurt to lower the amount of milk needed for butter significantly. I cant think of a proper number, but i guess everything above one liter isn't worth making butter fep wise.