It's OK to be selfish every now and then. You taking a short trip to see a good friend AND as a bonus see a concert you'd like to see is something YOU have earned.
You work hard to provide for your family....YOU found another way to provide even more money from a second source.
Why is it ok for your wife to go out and buy specific things for HER diet...but it's not ok for you to do something like this for yourself? I realize that the amount she spent on those olives...most likely wasn't $200....but dieting IS expensive. Buying specific foods for diets...adds up and gets quite costly. I know, I'm currently working hard to eat very well...and it's a lot more expensive at times than eating quick, pre fixed, higher calorie foods. I imagine if she added up what she's bought "for her diet" specifically...it would easily match the $200 you want to spend on yourself, but it's ok for her to do this for herself?
She may justify what she's doing as "non selfish", but it IS something she's doing for her...YOU are entitled to do something just for you too! Don't back down on this. Every penny the two of you earn does NOT have to go to something for the children or the family. It's not right of her to expect you to work your butt off to provide the money, but then not get to enjoy the benefits of it from time-to-time.
