GTGT and spcm,
If you want to equate this to a car sale, than I want the same ability I have in a car sale. In a car sale, I can take the car (or bring one with me) to a mechanic to review the true state of the car, i.e how the engine is holding up, how the brakes are, the wear on the tires, etc. Then I want the ball to take to a Pro Shop to have checked out, looked at under that product to view the surface, etc to prove to me the ball is as was advertised. Oh wait, can't do that can you....would either of you ever buy a car without seeing it first, without inspecting it first? I doubt it.
In the case of a bowling ball, the seller is advertising the ball in a certain condition, number of games, etc. Any use of the ball once the ad is placed, changes those conditions. If the seller does not update his ad, than basically he is selling the item under false pretenses. It may have double or triple the number of games on it over what was stated. And, in terms of bowling balls that makes a difference. Would either of you pay the same price for a ball with 60-70 games on it as you would for one with 20-30? I think not.
Bottomline is, once a ball is placed "For Sale" and the ad is published stating the condition of the ball, any use of that ball, without updating the ad, is unethical. You are basically lying to anyone who trys or does buy that ball. People complain all the time about how people want to buy used balls for next to nothing, don't want to pay a fair price, yet I bet they would have no objections to what this seller did. Why would you expect buyers to pay a "fair" price when you as a seller aren't giving them a "fair" deal?