You may have been sold a QF/BA "DREAMTIME" or "DREAMTIME PLUS" fare.

These are a good RTW products but should not have cost anywhere near the price of a OW Explorer. They are not OneWorld RTW products and if they were sold as such then you have reason to be compensated.

You can verify the cost of the Dreamtime product be asking another travel agent, make sure they give you the price of the M class version as there are multiple classes it can book into, each has a different price.

If you have access to the tickets then have a look at the far basis code, this will allow you to see what sort of fare it is (or ask the TA for the fare basis). For a Dreamtime Plus it could be MJBBGB.