The need for a scuba compressor has occurred to me as well, but I was telling (lying to) myself that I could probably live without one. I notice you mention that your boat is wood construction, which I believe has it's own cost/maintenance considerations, but that aside, do you mind if I ask what your other annual costs runs?
I figure about $10,000 a year for moorage, insurance and non running maintenance (bottom paint for example) before I even turn the engine on. That is CAD. Because it is wood I have it in a boathouse which roughly doubles the moorage, but halves the maintenance topside. Sun and weather is hard on a boat and destroys a wooden one.
I do all my own maintenance so keep that in mind. Contrary to what most think a wood boat does not require much more maintenance than a plastic one. If it is out of the weather and you know how to take care of it. Don’t think I have done very much at all to this one that I would not have done to a similarly sized fiberglass boat. The exception is brightwork (varnish the topside wood) but in a boathouse that is a once every five year task. Outside it would be every year.
The most expensive part of owning a boat is not the purchase price it is the ongoing expenses. I paid less than $20,000 for mine 15 years ago and $150,000 - 200,000 to park it and keep it running over that same period. A newer boat would have been much more to buy but the non running maintenance would be about the same. Then running expenses fuel, and maintenance on top of that. Metal bits that are in contact with salt water don’t last. New risers every ten years or so, raw water pumps, toilets and holding tanks and plumbing etc etc...
Larger boats burn WAY more fuel than a smaller boat. A small planing hull is reasonably cheap to run and moves fast. Larger hulls that do not plane are not fast and burn fuel. I get roughly 3 liters a knot at 6 knots 6 liters at 8 knots and then it gets crazy. At top speed - about 15 knots it burns about 35 gallons an hour. Only used to get through passes against current and the engines are not happy to be worked that hard.
A newer lighter fiberglass boat is better on fuel and you can get larger boats that plane so are a bit easier on fuel. Diesel is better as well but more expensive to buy and maintain.
On the compressor issue you are just hooped. To dive every day you need a tank for every dive and diver and then either return to where you started where you have a vehicle to take to the fill station or a compressor onboard. Fill stations are not conveniently located. For a small fast boat you can run out for the day and come back and refill. A large boat is not going to work for daily diving without a compressor. You just can’t get very far away from a fill station unless you are prepared to carry tanks for multiple dives. You also have to figure out how to get tanks from the boat to the fill station. NP at your home marina, big problem just about everywhere else.
Hope all the rambling helps