Under $50 for a scope? Hmmm...
You'll probably get a lot of advice that you need to spend at least a couple of hundred, but if you're like me and haven't got $250+ for a scope, that's a whole different story.
Several people have commented that they've had luck with a Simmons 8-Point, which sells in the $40 range (check eBay). I've also read that the NcStar scopes are okay.
The downside to this is that a scope in that range is at risk for failing when you need it most; lots of anecdotes about reticles breaking, lenses coming loose (I had this happen on a cheap Tasco that came with a used 30-30 I bought), not holding zero, etc. etc.
If it were me, I'd look for a Simmons ATV--they're closer to a hundred, but you might luck out and find a gently-used one for less. For that matter, fixed-power scopes are out of fashion; you might be able to get a good quality used 4x scope fairly cheap.
Put another way, going with a low-cost scope can be a hit-or-miss proposition--literally.