I always find it instructive to put things into economic terms.

By your example, assuming a labor rate of $30 per hour, the labor alone would be valued at $720. Add in the cost of material, (and I admit I have no idea what wool thread costs) and I'd not be surprised to see the cost exceed $1000. If there is a retailer involved, the price would increase again.

Now my point is that, while the figures involved may have been smaller, the value, in absolute terms, of that fabric in pre-industrial times would have been comparable. A length of tartan fabric is now and always has been a significant investment. Is it any wonder then that plaids were so often repaired and repurposed.