How much would a tender of coal cost? Come to that, how much does it cost to hire a loco in the first place?
Coal costs about £400 per tonne. The coal capacity depends on the design of the loco i.e. half a tonne for a very small industrial shunting type , seven for a black five. Loco hire rates are subject to negotiation between the owner and the hirer, there's no defined scale of charges but usually if it's a long term hire the daily rate is lower than ,for say, a weekend hire to cover a gala. Ex industrial types are cheaper than those from the railway companies. By way of example a class 4 type on long term hire costs in the region of £600 to £700 per steaming day. An ex NCB Austerity would be less but not by much. From the owners viewpoint setting a daily hire cost for a steam loco is something of a shot in the dark as over the nominal ten years between major overhauls repair costs can increase for all sorts of reasons. There are no profits to be made! Also some railways are much kinder to hire locos than others. The intention is that the loco , one way or the other, must earn enough in this ten year period to cover the costs of repairs and overhaul.
Locos usually arrive by road with whatever coal is left in the bunker / tender after the last steaming. This will not be a lot, sometimes nothing. The tanks will be empty but, depending on the size , not always the boiler.
To the above costs must be added that of transport to and from the hiring railway that again fall to the hirer. I can't quote any recent costs but think in thousands.
This is why steam gala ticket prices are so high!