One of life's irony

I went to the chicken shop today and bought 3 pieces of fillet meat. It was just under a kilo. Noticing the price that says "$7.90 per kilo (min.1 kg)", I asked for one more piece of fillet. Instead of paying for the extra piece, I was given back $0.85 instead. I didn't need so much meat, but I have to take more in order to pay less. Ironical.