Adsense Discrepancies

I've noticed that things aren't quite adding up lately.

I'll be watching my Google analytics, and see that I'm getting say 2,000 unique visitors one day with 5,000 page impressions. Then adsense will say for that same day that I'm getting 4,000 page impressions. hmm...

Also, today I've noticed that my total revenue is $xxx.xx so far, but when I add each of my channels numbers up, it doesn't add up to the total amount.

Last time I spoke to Google about the discrepancies, they managed to confuse the heck out of me about analytic differences, and since GA, adwords, and Adsense are all different departments, they couldn't give me a straight answer. (My observations about discrepancies in analytics extends to Adwords and GA too.) Doesn't seem that any one person at Google knows about knows enough about 2 or 3 departments.

Should I just give up and let things role on, whether in my favor or not? Is it possible that the discrepancies really are not in my favor, and I'm being screwed? I know this is a delicate arena because everyone is afraid to question how this all works because of fear of losing the green check each month, but I'd love to know that it's working correctly at the very least.

Any and all thoughts are appreciated.