MC salvage yards sell used tires all the time. The are priced in the 20 to 50 dollar range, depending on the tire and condition. All new tires now come with a mfg date. The common sense is looking for tires that are not older than 3 to 6 years old. You still will have to get the tire mounted and balanced. I'm looking into tires myself at the moment and even though I have access to a MC salvage yard inventory, I'm still looking for new tires... I found the Chen Shim tires to be in the 60 to 70 dollar range for my tire size. That's not much different than a high end tire found at a MC salvage yard. If you purchase a tire at a bike shop, you may be able to negotiate a discount on the mounting and balancing providing you bring in the wheel already dismounted from the bike. For me - I'll spend the extra 20 or 30 dollars for a new tire vs something used. I think my skin is worth that much.