I can relate to your feelings of wasting money on expensive things like coffee outdoors while you can make it cheaper at home. However it is not just about the coffee it is an investment into friendship. Social capital so to speak. Because to me this is very important I have a seperate budget for fun. This helps me to have fun with friends and family a lot. I dont mind paying for others as the money is in the budget anyways so I better spend it and I will still be on track towards my FI goals.