I've found that the exact match keyword has the highest conversion rate in almost all circumstances. So it would make sense to have a higher max bid on the exact match then phrase or broad batch. Even with lots of negative search terms to maximimize conversion on the broader matches, if the bid is the same as exact match, the cost per conversion will be much higher (too high.)
However in chatting with an Adwords Support Rep (on a different matter) they stated after looking through my account at the end of the chat:
" duplicate keywords will impact on quality score. your all keywords will compete with each other"
However many of the ad groups in question these duplicate keywords have quality score of 9 and 10. So obviously if there is an effect it seems it may be minimal.
I thought it was pretty common for people to bid higher on more exact match and lower on more broad match. What's the real story here? Was this support rep not seeing the big picture?