erin, I wonder if that is because your photography is so consistently good? For us, half of my photography is good (the half I paid someone else to photograph), but the ones that I did myself are not generally good enough to get decent clicks for (and the clicks I do get are less likely to convert).
definitely important to limit the bid price; I set them well lower than Etsy advised and still make okay $ with it - maybe 5% of total sales, but it's pretty cheap and 5% is 5%, after all.
If I could find another advertising platform that was as easy to use and as good a ROI, I'd do it in a second. (well, when I have a free second, anyway)