Hiya Jed
I had an economy OWE issued in Australia and was to be charged to aud200 to completely reroute it. Not just one or two changes here and there but a complete reroute from eastbound travel to westbound.
As an aside there is no cancellation fee for the OWE so if you simply cancel the old ticket, which is what I did, and pay for the new one upfront, you will not have to pay a rerouting fee. The only drawback is you have to bear the cost of the original ticket until the airline refunds you, which I have been told can take up to 3 months.
Regards