Hi - Mine is 2000 rpm, I got it about a year ago though. I took a look at the WalMart site and it looks like they have discontinued that one. I did find this Skill for under $30 though:
Here's a 0-2,500 rpm Hitachi for $20
According to Kreg you should use a 2000+rpm drill. All the cheaper ones seem to be topped out at 1200 to 1500 rpm. What rpm is the $20 B&D? I can't find a corded B&D on walmarts site.
I use a corded Makita hammer drill (with the hammer feature deselected) which is pretty much dedicated to the Kreg step bit as I seldom need it to drill concrete. I get cleaner holes than with the cordless & don't have to switch bits. To drive screws I use a 19.2 volt Craftsman. Both drills about 4 yrs old.