Prices start from the smallest standard size in oak. Ash is the same price; walnut trim adds about 8%.
Because nothing is made until you order it, the timber has to acclimatise in the workshop for two weeks first, and the oil finish needs four coats with a day between each. We could hold stock and ship in three days, but then we would be a different company selling a different thing.
Yes, and up to about ten per cent off a standard size there is no extra charge. Beyond that it is quoted, because it usually means a different board layout and more waste.
Oak and ash both move, which is why the tops are made with breadboard ends and the panels float in their frames rather than being glued solid. We build the movement in instead of pretending it will not happen.
Fifteen years on the structure. In practice we fix most things for free well beyond that, because a repaired table is a better advert than a replaced one.