Well, frankly, your choice of titles baffles me.
I'm shipping from Canada, so shipping cost is very important. Your listings have an average of $27-28USD ($35CDN) shipping cost.
That's because from the look of things they are coffee table books. Not only are these sold as gifts (not to people who buy them on purpose) but they tend to be large, heavy, and low information.
Pay attention to the books that sold.
Going only by feedback, there were three books on gardening, one on Mormon catechism, and one ebook on email selling .
Keep in mind that for secondhand bookstores, bestsellers aren't.
And any books (like the Time-Life series) that were sold by subcription have little or no secondary market.
You need to specialize.
On this ID a few years ago I was selling publications by the British North American Philatelic Society. These titles were extremely esoteric and had a small potential audience, but I was one of the two sources world wide. (The other was my husband. 
) Although these were expensive, priced from $50 to $300, there was a demand and I did well with them. We sold the stock to a client when we retired and moved.
On another ID here, I sell vintage science fiction and fantasy, some theological criticism and some gay literature (on consignment from a friend who was financing his husband's immigration to Canada). Also Bescherelle.
FWIW, the religious titles have the worst customers. YMMV.
My advice is :
Specialize in something hard to find.
Pay attention to what titles sell and find more.
Don't be afraid to donate turkeys.
I found I needed to get my listings over 500 when I closed down for a couple of months while moving, to get back to where I was selling before retirement.
Books are slow sellers. I have sold books that I have had in stock for a decade. So watch what you pay, and how much you are spending in listing fees.
Oh yeah, social media.
I added Facebook to my advertising mix about a year ago.
Good thing-- it's free.
Bad thing-- it takes time.
Bad thing-- not a single sale or enquiry in a year.
