I can only find Tetra Pond Aquasafe, so I will assume this is what you mean by "Pond Safe." It seems to be much the same as the regular AquaSafe, though they do not list ingredients, but it performs much of the same tasks. Odd that they should be priced differently, but maybe that is just because the "pond" bottle is larger so per volume it is less expensive? Most conditioners are similar. I buy the 2 liter jug of the one I use, which happens to be API's Tap Water Conditioner.
One has to be careful of the ingredients, as some of these products add things like aloe vera which has no real benefit but has been shown to affect fish gills. The other thing to watch is how much you need per volume. Having to use more of a less expensive product may not be less expensive than using less of a more expensive product, plus you want to use less for the sake of the fish. All of these substances added to water get inside fish, and the less the better.
Byron.