I don't know about other people, but if I have a party for one of my kids, (or had, my oldest two are 24 and almost 21), I paid for everything for those invited. It included the venue, if not at my home), food, drink, cake, etc. and usually some type of take home item. I usually did not do goody bags but a craft or more for them to make and take home.
Depending on the friend and how close of a relationship my child had with that friend would depend if they were going to attend the party or not if they had to pay $20 or $30 dollars to do so.
I cannot imagine inviting someone to a kid's birthday party and expecting them to pay $20/$30 to do so and bring a gift yet?
No, I don't think this is the norm anywhere.