Many of the paid staff roles tend to be those who work in the boilershops and other heavy engineering areas. That's not to say they have volunteers, but you'll find many of big railways will have a core team of paid staff to carry out maintenance and specialist work. It's a small and niche industry so the wages have to be competitive.
So it can be understandable if large sums are money are used to pay staff.
Maybe it's time for the heritage sector to have a major overhaul, and a real rationalisation of the number of railways. Hate to use the term, but maybe a Beeching Report for Heritage Railways.
A need to professionalise operations and meet ORR regs means that safety management competence is vital for all roles, everyday not just when there is time.
Some of the heritage railways are already mutli-million pound businesses and maybe it's time that more, if not most of the roles are done by paid, contracted staff. Many heritage railways are in rural and coastal tourist areas which are crying out for decent full time jobs all year round, supplemented by seasonal paid staff.
I'm not sure that a mutli-million pound business whose business model relies on not paying the majority of its staff or providing few, if any benefits is particularly ethical especially if those staff are expected and treated as if they are paid and contracted employees. In some cases it seems that volunteers are expected to pay for overnight accommodation at their own expense in railway provided hostels.
A better focus on what the fare paying passenger wants rather than throwing thousands of pounds after sentimental projects that might never come to fruition. A yard full of rusting rusting and decaying scrap locos and carriages being kept forever in the hope they might be restored is not only wasting space, missing out on some scrap revenue but often detracts from the experience that most visitors come for.
Relying on volunteers to run a railway isn't sound, as this thread started out talking about. It's only a dedicated bunch who are happy to turn up very early in the morning to a prep a loco or work a train late in the evening in the pouring rain.
Many people on railforum are quite happy to froth at the mouth when the big railway has to rely on volunteer train crew to run Sunday services on some companies, and while they are different beast, a network and operator needs to know it will have people available to run that timetable, which with volunteer labour isn't always possible.
I can forsee in the next 5-10 years the number of heritage railways being drastically reduced as many no longer become viable for various reasons and only a few big players being left.