Wendy,
Right now, I'm on a quest to double my income. (I'd really love to minimize my student debt, and I'm thinking etsy can help with that!) Right now, my average sale equals about $18, I'm in the process of expanding my shop so that the average sale is around $40 or $50. I'm adding necklaces to go along with my earrings and presenting a large inventory (that I know will entice my target customer) so they'll consider my tiered discounts like "buy 2 get one half off" or "buy 3 get one free", etc.
Perhaps you can interlock items in your shop so that your description suggests that if they buy this they'll "NEED" this also cause they go perfect together! I think customers like to see that merchants have sort of thought things out for them already :) Or maybe you can photograph grouped items so it'll attract not just vintage lovers, but people who enjoy eclectic/quirky décor.
Hope this gives you something to think about!