I learned a lesson a long time ago; you will get more serious inquiries to an add if you list the price you would like to get for an item.
I'm sure a lot of people have had a lot of luck posting obo or what's a fair price, but in my opinion you are fishing for turds.
If I'm going bass fishing, I will take bass fishing gear. Trout= trout gear, walley = walleye gear and so forth.
If you are seriously wanting to sell something ask for it. However, just because you ask for it doesn't mean you are going to get it.
If you are wanting to sell an item then sell it. If you just want to masturbate and fantasize then go take an extra-long shower.
Paul Watts himself will tell you on his website not to expect to recover tuning costs. It doesn't matter who tuned a gun or how they went about it. Unless they used solid gold, platonium and the ever elusive unobtanium, don't expect to get your money back.
I have a revision to an old saying; "you can jack yourself off, but you can't jack your friends off."
I understand that this may offend some members and may affect my membership to this forum, however it is my understanding that this forum is here to further the sport of adult airgun shooting. Let's focus on that and remember that most of the guys here are here for the sole purpose of supporting one another. Also keep in mind that you may get a really good bite from someone new to this site; great right? Well what happens if this new member find out that you screwed them, intentionally or otherwise? They go tell their friends. No big deal right? Anybody ever work in retail? The best advertising is word of mouth. You can spend all the money you want on the biggest billboard on the busiest street, but *_*_*_*_*_* off one potential customer and you've wasted every dime.
If your intent is to prosper find some pimply faced kid at your nearest high school. If you want to aquire some "airgun money" then take a deal, regrdless of how much you win or lose, and gain a new friend, hunting buddy or accolyte into the world of adult airguns.
Bottom line is: ask for what you want, then be prepared to compromise.