It's a fine line to walk, between being a true folkie and trying to make money. When money rears its ugly head, it sometimes happens that even folkies forget themselves and fall victim to mercenary motives. And, with money comes a number of ego games. Professionalism and courtesy, as difficult as they are to define, are the best approach. I don't see that either of them means you should promote others at your expense. If you're doing promotional things you should be getting paid. Reciprocity can work, if it is indeed reciprocal. There is also a common problem of tacit or unspoken assumptions that turn out not to be mutually understood. That's a communications error. Bottom line, if what you're doing isn't making you feel right about doing it, don't do it.