It really does depend on how thorough a job you want, and where you get it done, and to what standard. You could quite literally pay anything from £1000 to £10,000+.
Do the scratches go right through the clearcoat? If not, you might consider having the paint polished. You'd be amazed at the defects that can be removed and the transformation that can be achieved.
Much cheaper than painting
.
Cliff