Hi,
Ultimately a detailed form analysis approach needs to be applied. Eg beaten three lengths in an Open Handicap held up until the 100 and then running on strongly is far superior to being beaten one length in a restricted event having the run of the race.
Class does not equal prize money won - in preparation of Pro-Punter information we never even look at prizemoney won.
If you do a forum search you should find a big thread about prizemoney and class.
Hope this is some help.
Neil.