When I say 'end user' I guess I am talking about the sheer amount of Javascript loading and computation they no longer had to put up with jumping through waterfalls. Header bidding fixed that which meant that javascript based ads loaded in a significantly more efficient and sane way. Privacy, etc is obviously a different issue.
Don't be dense. If you pay $5 per conversion, and earn $10 per conversion, you make $5 profit as an ad buyer. What happens if you have 2 conversions? 3? 20? You make more profit.
Alternatively think about the flipside, how in the world could you possibly think having a lower conversion rate is good for the ad buyer? A 0% rate?
If you pay $5 per conversion, it doesn't matter if you have 100 impressions per conversion or 10 impressions per conversion. You are pretty conversion rate insensitive.
I mean, obviously it's different at the extremes like 0% vs 100%, but I doubt header-bidding produces that great an effect.
I’ll just ignore the part about what you said about end users other than to say it’s arguable.