What's your optimal ROI?

At what point did you stop increasing your bid?

[blaze]

My advertisng costs for an intangible product are about 30% of my revenue. Given that my overhead is minimal, I end up with a 70% profit margin.

I have increased my bids, but so far it's been done in a clumsy way and I've increased my revenue but decreased my margins more, so net effect didn't increase my profits.

I am wonder what other people are seeing as an optimal margin / ROI for their AdWords campaign and intangible products.

[Michael Anthony]

Mine varies dependent on the product - from a loss to over 800% ROI.