Oracle does cost 35% more than Stonehenge, so it makes sense for it to be more powerful.
Stonehenge would still retain the 1

1

that all wonders have. Consider that 3rd ring tiles take a long time to expand to and are
very expensive to purchase, at 200-300

apiece. One example of when this would be useful is when sea resources are in the 3rd ring. Other cities usually can't pick up those resources. I could also give it a second unique effect like a map reveal to a 10-20 tile radius, world map centering, or so on.
I basically just want to make sure each wonder feels useful for at least some specific strategy. The effects are too different to make numeric comparisons.