I am incurably "value oriented" (please, I'm not cheap! <grin>). I am always on the lookout for something that will do what I want for less money than the "standard issue".
One of the more difficult processes of building speaker enclosures is making nice round holes and recesses for flush mounting drivers. I have cut many a hole using my jig saw and a handful of holesaws and I was ready to move to the next level. I had been eyeballing the very nice Jasper Circle Jigs and was trying to justify spending $50 for the pair of them to cover all my hole cutting needs.
Searching the Net for alternatives, I found ones that were either for cutting very large circles, as in table tops or were more expensive than the pair of Jasper Jigs. Finally, one of the last places I checked, and should have been the first, was SEARS. A bit of digging in their web site netted me the generic-sounding Sears Multi-Purpose Router Guide Kit. I stopped by the local Sears retail store and picked one up, not really knowing if it would accomplish the required tasks, but it performed quite nicely. Total cost: $20.
I have not used the Jasper Circle Jig, so I cannot offer a comparison, but this Sears attachment will cut holes and recesses from 2 1/4" up to 24". If you modify it as I did by cutting away the section of plastic rim at the pivot slot, it will cut smaller than 2" diameter. It will also allow you to cut slots, bevels, edges and contours (haven't tried any of that stuff yet).
I think the biggest difference between this and the Jasper Jig is setting it to a certain size. The Jasper seems to have a pivot hole for each specific hole diameter. With the Sears Guide, you have to measure from the pivot pin to the outer edge of the router bit (hole radius) and then double that number for the hole diameter. It takes a bit of fussing and a trial cut or two to get the size just right, but once you have it set it repeats quite nicely.
The box claims it fits all Sears fixed-base routers. I have and older Sears router and it bolted right to it.