Whenever I feed a leveled up monster, it takes too much food to level it up.
For example, for my 3 star level 104 Rabidex, the bar shows it needs 43200 food to gain a level, but it takes 40500 food per click for a total of 202000 food for leveling from level 104 to 105.
Is this a known problem ?

@Divyansh-Gupta It is not a problem/bug, it is programmed that way, the amount shown is for 1/4 of the total food required.

And if you think a 3 star is expensive to feed, wait until you get a 5.

And for further info you can check wiki
http://monster-wiki.com/monster-lab/food/