Darned cheek all round in my opinion. I suppose it depends on how gregarious you are, but I personally hate it if someone invites someone else along. I used to have a friend, years ago, who did this. One day when I thought we two were going bowling I found out that we were picking up four other people to come with us to make up a team.
I was so incensed that I made her stop the car and I got out.... in the middle of nowhere as it turned out and I had to get a bus home. Serves me right I suppose. But I still hate people who invite other people without any explanation beforehand.
As for the money/voucher side of it, well, words fail me.
Also, I've just remembered... One of my sons used to date a girl who played in a brass band. One day she turned up for a date, - accompanied, but un-musically - as it were, - by the whole band. The romance didn't last long!