does anyone else find this weird?

My bfs parents own a catering center that also hosts small parties. My bfs grandfathers bday party was held there. Obviously they had to hire someone to cook and serve the food. In total there were only 20 people invited with 4 of them being children under 5. Since my bfs parents own the place and hosted the party I find it strange that they had me pay $50 to attend but as well as their family members were also charged. My bfs family are financially secure and have a successful business. They also planned the party when they know there family isn't as fortunate nor am I as a student. I just find it very odd. When my parents had my family go out to dinner for my bday they paid and if the party was at my house they also would pay. What do you guys think? Isn't this sleazy? Especially since they could have cooked their own food and just did a buffet to help everyone else save the money. Also forgot to add it was held on a weekday so it's not like they lost a day of business or anything. How tacky is that? I felt obligated to go and didn't find out the cost until after I said I could go and it was too late to bail.