That BSA may look OK, and may even zero OK now.
But what the extra money for a Leupold pays for is good eye relief, durability, good optics (no distortion of the image), better light transmission in low light situations, consistency of adjustments, a lifetime warranty, good customer service, and last, but not least, a fair wage to the U.S. employees of Leupold and Japanese subcontractors.
I am guessing you don't have a good scope, or you wouldn't be posting this question. To continue the analogies, why buy an expensive stereo system for your home when you can get a radio from your local discount outlet for $20? They both pick up radio stations and play cassettes, right? Why spend the extra money? It's just that with the example of the stereo, you can SEE that it is a cheap piece of crap.
Having said that, however, I will readily admit that not everyone needs a Leupold, Burris, or Swarovski. Many folks can happily make do with a Tasco, Bushnell, or BSA (heck, I have a few Trashcos and Bushnells myself). Just rest assured that there *is* a difference.