Is $50 a month really something to worry about? If you got even one referral from attending one of these dinners, wouldn't that lead to a decade or more of "$50 dinners" in fees? If you're going to be a business owner and entrepreneur—and that's what being a partner at a law firm is—you have to escape the employee mindset of "I shouldn't have to pay for anything work-related." Sometimes you have to spend a little money to make some money.
Regarding the leadership position in the bar association, just do it. Most such positions are temporary, and while they're a minor pain in the butt at the time, you can put it on your website/resume/etc. forever. Even if you slack off and do the bare minimum, it's still a line on the resume.
Eventually, you have to figure out which marketing strategies work best for you, and which ones are "worth it." And remember, once you have enough business, you can do whatever you want. That is the secret of private practice that most younger lawyers forget—you have no power unless you have clients.