I have an XP100 that I have just discovered some bbl. pits in. What options do I have, and what do they run price-wise?

When you say barrel pits, what do you mean? Are the inside the bore or chamber or on the outside of the barrel? If the are an the inside there's not much you can do. If they don't affect accuracy then don't worry about it. If they are on the outside and it bothers you, an experienced "smithy" might be able to MIG weld up the pits, grind them down flush and re-blue. That could cost you up to $50-$100.

On the inside. As far as accuracy, I don't know, I haven't shot it.

If the bore is pitted, then its likely there is still some rust in the pits. Sometimes it looks worse than it really is. Try this:

1.Take a cartridge case and cut it of at the shoulder.
2.Drill through the primer pocket with the largest drill size that won't touch the inside of the case.
3.Find a 12-15 inch length of plastic tubing that will fit snugly over the cartridge rim.
4. Find a funnel that has a tip which will fit in the other end of the tubing.
5. Take a big kettle and boil about 2-3 quarts of water.
6. Put some gloves on and hold the gun. Place the cartridge end of the tubing in the chamber, then slowly pour the boiling water through the funnel and let it drain out the end of the barrel. Try to make the pour last about 5 minutes.

What this will do is convert the rust to a softer form wich can be removed with a bore brush - much like rust-blueing. Take your bore brush and "card" this rust out. Run a patch through and you'll probably see reddish brown stains on it. Finally, wrap a patch around an old bore brush and use JB paste or another bore conditioning product to polish out the bore. That's probably as clean as you're going to get it.

Next, shoot the thing and see if it's accurate. If it is, don't worry. Usually if the rifling is good and sharp it will shoot well.