Swarovski buckles vary in price depending on the size of the buckle, the number of crystals used, colors, pattern (single row or accent vs. pave' set or total encrustation), the metal of the buckle, and other factors. But a variety of very nice buckles can be obtained in my area in a number of styles and patterns for $40 to $80. You'll see prices in the $100 to $400 and up range as well, but those are generally ones being sold through boutiques or as designer items rather than those sold by suppliers.
I'm not sure about the optics--they may be from the same parent company, but different branches? Couldn't say for certain...
I do like the Swarovski "rhinestones" because of the quality--if it is a genuine Swarovski rhinestone, it is going to have a lot of fire and a good cut. This makes the prices higher than for just a "crystal" buckle, but those are hit and miss as far as quality. I've seen some off-brands and imports that just looked awful--no life to the crystal because the crystals were cloudy, poorly cut, and indifferently set. And I've seen some non-Swarovski buckles that had good crystals and a good set as well. It just depends, I guess.
By the way, you can also get spots to set into the belt leather as well. http://www.standardrivet.com/swarovski-elements/mounted/133-mounted-brilliant-swarovski-crystals.php for instance...