I have done it once (at a cost of about £60). But I feel that most of the time it is not worth it. By the time the outer sole has gone, usually the goretex and leather are also decaying and in some cases (depending on the boot) the midsole is also not in great shape.
So usually I just buy new boots and demote the old ones to dayhiking/ fair weather shoes, or just for walking through town. For many walks you don't need much of a thread and on dry ground and with reasonable weather you don't need them to be waterproof either.
But on multiday/week/months walks in wet or rocky area or in snow and real mountains, I really want to walk on boots that are in good shape, including the midsoles. So that's what I use new boots for.