i don't see what's the point of all these "how's that possible", or "is that normal?" threads, if you didn't do anything blackhat or against TOS then why worry? If you are worried, contact google. Coming here and whining about your $800/day achievement is lame.
Report this to google else you are sure to be banned.Anyways you are too lucky to make atleast $200 per day.
If the traffic on your website is same and you haven't made much changes to your Google Adsense Ads, I would suggest you to contact Adsense team
Mine was $120 for the best day. I want to really make it into the large amounts with huge networks of sites.
It may be that your account has been activated in 'Ad Review Centre' and you have lots of advertisers. It is known that this increases revenue....if not get in contact with Google and let them know....you dont want to risk losing your earnings. $200pd is still quite large to lose.
If you dont mind me asking, whats your niche? If this is the case then it may be that your site has ranked VERY high for a popular keyword in Bing. If this is true then this is excellent news. Well done.
remove your AdSense ads for a few days; if you are under "attack" this might save both your web site and your AdSense account; your google analytics should give you a clue; if you have analytics and adsense linked together, check if your adsense revenue is coming from direct hits or from visitors coming from a search engine.
Congratulations on earning so much! Were the keywords that the Bing clicks came from related to a certain date in time, or did you just receive a one-day pop on Bing? (In other words, do you still rank well for those keywords?)