people say adsence the best service... i get $0.35 per click on average using adbrite on my warez forum as far as i have seen you adsence users dont seem to be making much with 20+ clicks
i think its normal if you have a good content and quality clicks then its normal you dont need to worry
congrats.. but you may check your impressions etc to smell foul play. It might be that someone clicked your ads multiple times. If your no. of clicks are same, only the amount you earned differs then its normal and congrats for that. I usually get $0.50 per clicks . ~$1.5 per click is normal for me..