I just meant that my current drop in sales on ebay may not be related to the change in postage at all.

i.e. According to my stats, the drop on Etsy, where postage is still $3, is 32%, and the drop on eBay is 38% (compared to same time last year). Nothing about that is conclusive, but at least suggests there's a possibility that the higher postage is actually having very little effect on my current sales volume.