I have organized regional USATF championship races over the last 10-15 years, and run in them for over 20. I absolutely love the local no-frills 5K. I don't need a shirt for every race I've run, or a medal, or some kind of gift. Sometimes I just want a start, finish, an accurate course, and a finish time. That said, putting these on has become a lot more expensive over the years.
The 'advancements' in running technology have created new costs. You pay a lot more now for these improvements.
Chip timing is more accurate and gives out faster results. That often is a flat rate (depending on the # of runners) or it can be a percentage of registration fee. The tech costs a lot more than the old school tear-away tags at the bottom of your bib.
Online registration, instead of paper registration with a check or cash, also costs a percentage of your registration fee (Or it is added as an additional fee - either way the runner pays for it).
Technical shirts instead of cotton - a shirt can cost up to $10 to produce and print, depending on the type of shirt (technical v. cotton), type (long sleeve v. short), and printing (both sides, color, etc...).
In addition, the 'usual' costs have also increased with inflation.
Depending on where your race is, thanks to the Boston bombing, the police in the Boston area now staff these races with a lot more officers. Races pay for that in 4 hour increments, and for every two officers there has to be a lieutenant.
Permit fees, facility rentals, equipment rentals, and ... porta potties. Those costs have increased markedly.
You can still find the local race that is relatively inexpensive. DanM mentioned Lone Gull (USATF-NE 10K Championship) that was held yesterday. Those organizers did a fantastic job. $35 got you an accurate course, a free short sleeve tech shirt, and some good food (scrambled eggs, french toast, donuts, bagels, cookies, breakfast pastries) at the end.
But, you may also recall that there were maybe two police officers, and two park and rec folks who worked the beach parking lot. It was a very 'simple' race in that regard. Not a lot of frills. And not a lot of added costs. Which is fine!