Sigificant Variance in PPC Cost

Is this normal?

[cabbagehead]

I'm looking at my cost of customer aquisition costs for both Yahoo and Google and its interesting to note that the cost per new customer varies by as much as 70% from day to day! I mean, it has gone from 69 cents to $2.15 from one day to the next. Incredible variance! Is this normal or an indication that something is wrong?

[eljefe3]

I'd look at a longer period of time ( if you can afford to) and get an average. Some days I make few sales on some items, then other days a lot, so it makes sense that this would be the same in what you are referring to.