Rip-off

I saw a cool T-shirt yesterday for only $10, but at the counter, the cashier asks me for $20. I say "But it says $10 on the price tag" He says "Ya, but it actually costs $20" So I give him the money and take the shirt. He says "Hey, you only gave me $10" So I say "Ya, it says $10 on the note, but it's actually a $50"