how come sometimes when I get 1 click i make 87 cents , but when I get 5 clicks in a day, the CPC suddenly averages to 0.26 a click ?
The rate changes. That's the fact. Sometimes the high cost advertisement appears on your page, sometimes the low cost one does. That is the real function of doing advertisement filtering (1 of the useful feature of google adsense)
I think in a span of a week there is sometimes a single day with the lowest CPC (that's what I experienced) it depends on the people interest and news that happen everyday, ad-filtering needs to be done to get more clicks with a high value.