I think it boils down to the friends really. I know people who when they offer me a ticket I assume I'm paying for it. Others I know it's free. Some people are more frugal than others. Personally if I had an extra ticket (already budgeted and paid for) I'll give it away. However I can totally understand the philosophy that just because I'm your friend I shouldn't have to subsidize your night out at the rink.
Either way, it should have been clear. But maybe if your friend is always a cheapskate he just assumed he knew he'd be cheap
