Group One Races

I notice that the NSW Trotters Derby and Oaks are for a total stake each of $40,000 .
With all the money available for stakes in NSW how can these be graded at Group One with such poor stakes offered??

Surely raced named Oaks and Derby should be Group One????
Surely the minimum at Group One should be $100k..??

See SA pacing derby and oaks. This subject gets debated every year.

See HRA guidelines for group racing and in particular the 50% rule that applies to Trotters.

http://www.harness.org.au/hra/feature/gr_glines.pdf