I note that several posts mention they can't afford it. The price is pretty steep for young working people and retirees on fixed incomes. Members, and especially Life Members, ought to be given a discount and first dibs on reservations. Beyond that, perhaps a lottery system could have given away a limited number of tickets.
Most attendees will need to stay overnight in a motel which will add greatly to the total.
Maybe change the name of the event to, "Maine Two-footer Money Specials"?
As someone who participates in a lot of photo charters, I can offer the following background:
Generally speaking, most of the folks who attend photo charters are serious photography enthusiasts, who happen to specialize in rail photography....as opposed to railfans who happen to own cameras. You're absolutely correct in your assertion that the cost of a typical photo charter these days has gone beyond the means of the average Joe. It's not the actual charter fees that push it over the edge, but all of the travel and living expenses in addition to that. The T&L typically more than doubles the cost of the trip. It is not unusual for the total trip cost to exceed $2,000, and some can go way beyond that. Most of us who do these deals are older folks, who don't have any kids left in the house.....or never had any in the first place.
Some charters, such as the ones at the WW&F are offered by the railroad itself, but more often than not, they are organized by an independent charter operator, who is usually a very accomplished professional photographer. The most successful ones develop a reputation for putting their patrons in a position to get spectacular photos, and they deliver on that reputation most of the time. That's why they get repeat business.
Here's are a few examples:
https://www.railpictures.net/photo/719748/https://www.railpictures.net/photo/603703/https://www.railpictures.net/photo/507991/The charter operator will typically conceive an idea that involves a particular railroad and specifically lettered equipment. He/she will negotiate with the railroad for a specific number of days/hours, including all of the extras. The cost of a day of operation varies, depending on the number and size of the locomotives desired, and the number of hours of operation. Many charters will operate from 6AM (before sunrise) to as late as midnight....then do it again the next day. That often requires multiple railroad crews ($$$). Just to give you an idea, the Cumbres & Toltec Scenic Railroad typically charges $10,000 per day for one K-36 locomotive and one crew. Their engines are a tad bigger than our 2-footers. Want a 2-engine Cumbres Turn? That's a $20,000 train.
Once they arrive at a price the operator thinks he/she can sell, it is advertised, usually privately, to a known list of prior clients. If the operator can't get a price that is saleable, the project will be abandoned. Similarly, if the idea does not sell with the clients, the event will be canceled. The group size is typically between 25 and 50 people, depending on what the railroad is charging, and the size of the run-by locations. At a wide-open railroad like the C&TS, you can have larger groups without compromising the quality of the photo opportunities. Obviously, the cost per person drops if the group size is larger. At typical New England railroads like the WW&F, the photo locations are much tighter, dictating smaller groups.
If the event runs, the operator will coordinate closely with the railroad to create an operating plan that is doable, and which will hit locations with great scenery at the times of optimal sunlight for each location. They also have back-up plans in case the weather is bad. That's how you get shots like the ones I posted above. Of course, each photographer still has to execute on the shot. These things are definitely not for everyone. They require a reasonable level of photographic skill, some degree of physical fitness (climbing and hiking involved), and the ability to go with minimal sleep for a few days. They are photographic events, not railfan events.
As you might expect, the market for these charters is not huge. There are perhaps 200-300 people in the US who will do one of these per year. Perhaps half that number will do 2-3. Perhaps 75 will do as many as half a dozen. It's basically the same folks on most of them....the social aspect is a big part of it.
Fortunately, many railroads also do railfan-type events, with much larger groups, shorter hours, and significantly lower prices. For most people who are just looking for a fun railfan experience, that's a much more cost-effective approach.

/Kevin Madore