Cap shouldn't be based on pet tier. It should be static. Extra food is always a plus, even if it's only 50 per day. I wouldn't be opposed to having ways to increase it such as an upgrade system, but such an upgrade system should be like every other upgrade system in the game: it becomes harder to progress the higher level it is. Basing it on pet level would make it easier to progress the higher level it is. Very unbalanced way to do it.
Better yet, just have it be very difficult to get pet food from this system (rather than having a solid cap) so that people can progress in it as quickly or as slowly as they dare to set the rate of their kills.
Even better, have the meat be something that you can buy pet food with daily, where each food costs more than the last, and where the cost resets daily (like with sacrifices).
Let's say you kill one mob every 6 seconds. In a day, you'd kill 14,400 mobs. Whereas someone killing a mob every second gets 86,400 mobs per day. Let's say the 14,400 is worth ~50 pet food (possibly modified by upgrades to be higher). The person getting 86,400 might earn ~100 pet food in a day.
A formula that would fit this curve might look like:
EDIT: the previous formula had a mistake in it. New formula should be better:
meat_cost = 2 * food_bought ^ 1.5 + 100
With this, the 6-second per kill guy gets 42 food per day. The 1-second per kill guy gets 97 food per day.
Better yet, just have it be very difficult to get pet food from this system (rather than having a solid cap) so that people can progress in it as quickly or as slowly as they dare to set the rate of their kills.
Even better, have the meat be something that you can buy pet food with daily, where each food costs more than the last, and where the cost resets daily (like with sacrifices).
Let's say you kill one mob every 6 seconds. In a day, you'd kill 14,400 mobs. Whereas someone killing a mob every second gets 86,400 mobs per day. Let's say the 14,400 is worth ~50 pet food (possibly modified by upgrades to be higher). The person getting 86,400 might earn ~100 pet food in a day.
A formula that would fit this curve might look like:
EDIT: the previous formula had a mistake in it. New formula should be better:
meat_cost = 2 * food_bought ^ 1.5 + 100
With this, the 6-second per kill guy gets 42 food per day. The 1-second per kill guy gets 97 food per day.