I'd agree the $ for some of these small runs can be too steep and excludes most people who fit that category and it doesn't fit into their training priorities.
And now for a walk down memory lane... (cue up Springsteen's "Glory Days")
I had some great times in my younger days at charity/local 5ks. I had the benefit of growing up in a town with a very active running club, and as a high school kid was getting whooped in summer races by the 14:xx guys we all worshipped and aspired to be. It was a really positive running culture, and the guys who graduated from our high schools would take the time to cool down with us. This was also the late 90's, and the races were max $10 for members and max $20 for non-members; no fancy finish line timing with cross country chute placing pulling the bottom tag off your number. Running was a big part of my high school experience, and I have a lot of great memories of the local races.
When I got to be a faster-guy and capable of winning the summer races, they were fun because we made them fun. If it were a weekend morning 5k, I'd time the last 3 miles of my long run to coincide with the start time of the run. There were enough guys running in college around that you'd need to push sub-16 for a slower race victory, and the summer series became the arena for all local HS/College XC/Track grudge matches. We were all training, so it became fun to find the ways to make the races "competitive." Example: we'd agree on a pace through 2.5 miles, last half a mile was every man for himself, unless some punk tried to take the race out like a show-boat and then we'd collectively bury him and wait until the final straightaway to see who cuts it. We had fun, we all ended the nights with handshakes, and wished each other the best until we raced again at Intercollegiates.
My former high school the coach was the race director for most of the races, so I wanted to help him pack things up afterward and be a positive presence. I, at least sub-consciously, realized the positive effect of the summer races on my formative years, and I felt it was important to give back; I'd ask the local kids about their training; I'd check-in with the old-timers to see how they are holding up; I'd answer training questions from the newb runners. I enjoyed it, and it definitely helped my ego and confidence!
Post-college, AKA the transition to the real-world, I had the benefit of a local running shop giving me free gear to keep training and running similar races. I had obviously given up the Oly Dreams by that point (LOL - I was never even close), but running was a big piece of my life for so many years it was hard to make a full-stop "out of competition." I was probably breaking about even in the balance of $ in free-gear and $ for entry fees, but every once and a while I'd feel like a big-shot when a "big" marathon or half-marathon would comp my entry and 2x nights of hotel to run. The running shop was happy because they were getting free advertising (enough people thought "some guy winning a 5k by 2 minutes must be really good! I want to buy my shoes from the name on his singlet!"), but personally it was a positive way to transition out of a lifestyle I had spent over investing in for over a decade.
I have since moved and live in a place that doesn't have a positive community like the running club in which I came up. I run the occasional half-marathon if my friends talk me into it, but I haven't run a 5k in years because they all seem to cost $30 going to trivial things. I would pay that for the right charity, but most of the races near me seem to be going to some for-profit cause race organization that gives everyone the chance to get a chip-time and post-race-selfie rather than invest in a local running community.
So, if you're still with me...
To the "fast college runners" - run a few local races and be a positive influence on the up-and-coming high schoolers, but remember the big races are in late October and early November!
To "all those sub 16 guys" - burn it while you still got it, and have some fun! Call/email some race directors and say "I have a PR of [xx:xx] I ran in [some reasonable time frame when I was training a lot but isn't so far removed from now] and think I could increase the competitiveness of your [race distance], do you provide any assistance on race entry fees or have an elite division?" One of the biggest mental transitions for me post-college was to stop feeling like I'm slow because I wasn't a 13:xx guy and realize my new friends or colleagues or (important) single-persons-of-interest don't care what your PR is if you're capable of winning a race (or finishing in the top 20 of some 7,000+ person race).