Something that I was thinking about

The other day after I went to the practice in the circle I wanted to join, the seniors told us that they were going to go eat sushi (the one that spins) and asked all the other members if they wanted to come with them.  Although I liked sushi, I decided not to go because I didn't have much money and didn't feel like going somewhere else anymore.  This is were the problem starts.  Once I told my friends that  I'm not going, they acted like that they could not believe what I was saying.  They said to me, "Why aren't you coming? Don't you want to make friends with other people in the group?" Indeed I wanted to become friends with other people, but I just didn't have the energy to go.  Apparently, my answer made my friends think that I wasn't trying to be friendly enough.   So here is the question.  Were my actions inappropriate in the sense of being a good group member?  Should I change my attitude while being in a group just in this situation?   I would be very happy if someone could give me an opinion.