Participants get money for winning. The events are certainly worth winning in their own right.
The total point method is already used to break ties, though. It may not be 100% accurate but I think it's better than simply going by placements. When there are huge point gaps it's quite apparent that one skater was clearly better than another during the Grand Prix series. Such as when Joannie Rochette clearly outskated Julia Sebestyen during the 2006 Grand Prix and yet didn't make the GPF because Sebestyen had the two easiest assignments of the series and thus was able to place higher. Joannie Rochette was screwed over yet again the next season when Kimmie Meissner made the GPF with a much weaker showing.As for easy or hard fields, the total point method has problems, too. Besides the differences between stingy and generous officiating panels, in addition the scores seem to rise as the season progresses -- both because the performers skate better and also because of gradual grade inflation over the course of the season.