Cheapest is a Savage Arms Model 89. It's a SS rifle in .22LR, with a falling-block action, styled to look like a lever gun. Bought it for $30 in around 1987 or '88.
Most expensive was an Interarms-Walther PPK/S, in 1990, for just under $400, I think.
Actually, I did have someone give me a sawed-down Savage SS shotgun once. The stock is cut down, and the barrel down to 20 inches. I think I measured the overall at 38 inches, if I remember correctly. So, I guess that would be my cheapest, though I didn't seek it out.