Gods, that's a hard one to answer.
My (very) rough guess might be an average of four or five pages per 7 inch section, at least for such things as elevated railways. (The straight railway bridge has four pieces, plus the base tile makes five.) If you were to cover the entire board with railway that would be something like 220 sheets or so - quite a lot of printing (and most likely a wee bit on the high side... take that as your worst case scenario). More reasonably you are looking at a minimum of 49 sheets (7 tiles x 7 tiles.) for the base, which will make a board 49 inches on a side. And maybe a hundred more for props, bridges, vehicles, etc.
A more reasonable guess might be done by using the and finding out how many sheets will be needed after figuring out what you want on that.
Gothic Realms, that is even more variable, but again I would look at a high of four or five pages per seven inches, most likely less.
A cheat that I did for the sewers out of Gothic Realms is to make some geomorphs - a mix of 2 tile x 2 tile boards and 1 tile x 2 tile sections. The y can then be positioned as needed.
Sorry if this sounds discouraging - I think that you might be better served buying a better printer than running to Kinkos, since that would likely set you off less money in the long run.
(I have no idea how many sheets I have printed over the years, but likely in the thousands or at least the high hundreds, just not all at once.)
The Auld Grump
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