The difference in fare between K and H can be quite small. for LHR-SYD r/t the difference between K and H classes r/t if GBP150. Depending on the lowest class available at time of booking, it may be worth paying the extra

From the lowest base economy fare of GBP700 there is a fair difference between it and the GBP1463 for H class ( in March for example ) , but even there, is it worth paying GBP370 to save 59,000 points - but of course it is a gamble on getting the upgrade

I think that I will stick to 87,500 and be able to get the actual business ticket from AA on a decent carrier such as QR or EY