I have four side rulers, all of them I bought at antique stores. One of them, the Pickett N600, was used by the Apollo astronauts (it's small---6in (15cm) long, made from aluminum, and very nice). I think I paid about $10-15 for each of them.
i'm guessing you mean slide rules, and that the apollo astronauts used a slide rule of the same model as yours, not the one you bought at the antique store
the prices i see on ebay suggest you could sell most of them for significantly more than you paid; unless you have slide-rule-fancying heirs, try to do this before you die, because otherwise they're likely to end up in a dumpster
