I covered this question in one of my previous videos a bit, but questions are still coming, so decided to dedicate specific video covering this topic. On average I spend from 5 to 10 US$ a day on food training full-time (i.e. 3-4 hours a day). I believe it's not much at all and also, funny observation - I eat more when not training :D
Probably because I have more time to think about food :)