Welding and all measurable physical work is going through the roof price-wise, £10 per inch is not now uncommon.
I was quoted £200 for a small (40mm x 200mm) welded patch on the inner sill of my wife's 20 year old Mk1 MX-5, as soon as I started talking about job quality and "semi-restoration standards" i.e. not just welding a patch across everything visible the guy looked a bit ill - I did it myself as in a previous life I was a panel beater and worked in classic car restoration (photos on request).
I'd suggest buying a welding set and learning to weld, then doing it yourself, that way you'll have the equipment and the skills, if you pay someone else all you have is their invoice. ;-)