dependson your longterm views too, if the car is spanking mint and you want to keep it forever then ok its gottta be costly but if its the bottom section of the arch (if 5 door) and you see it as just a car then grind it back filler it up and paint it from a can (depending what colour)
i worked in a ford bodyshop and they would want a grand but i know people who would do just as good a job for £200 all in
im fixing up an escort gti for my mum and heres are goin the same way (5 dr bottom bit) ill be leaving it but if i wanted to tidy that up i'd clean then fill then paint it from a can, its state blue and easy to hide or could black that section, i could cut and weld it but its a 600 car so what bother
the chassis rails have been welded loads this year but i do like welding, the rest of the car is pretty tidy tho