Cheap? You wanna know cheap? Try a Tasco 3-7x20 rimfire scope that I put on my old Marlin .22LR rilfe. [:'(] I think the thing was like $12.95 at Wal-Mart or something like that.
I used it a few times at the outdoor range at the local WMA when plinking targets with my 17yr old twin daughters. After about round of 14 shots (tube fed Marlin Model 60 .22), the scope shifted back in those grooves on the receiver. I slid it back in place, cranked down on the screws with a Phillips screwdriver, and took some more shots. Same thing again... [:@] Then one of my daughters said that using a scope on a .22 is "cheating"!! And this is the same daughter who, er, well, um,
actually out-shot me on the range! 
[:-] Nevertheless, we took of the cheap Tasco scope and now use open sights on the Marlin.
Butch