Buying Used Books On Ebay, Selling Them On Amazon: Can You Make A Profit?

I've wondered for quite awhile if it is indeed possible to search out and buy book lots on Ebay, then resell them in the Amazon Marketplace for a healthy profit.
I know that the books are there. I just wanted to know if you can make money doing this.
So I tried it.
I spent about 45 minutes searching through used book lots on day recently.
Since I know that I need to buy my used books for resell at a discount, the best way to do this is to minimize the shipping costs and buy in bulk. That's why I searched on "book lots" on Ebay, and the results that came back contained everything from full book collections, to book sets, to 4-12 book lots that I could browse through.
There were quite a number of fiction titles (which don't sell very well on Amazon) and some non-fiction subjects which don't sell real well (run-of-the-mill cookbooks or diet books).
But I did come across some non-fiction UFO & alien paperbacks (these always seem to sell well for me). So I dug deeper.
I found an Ebay auction offering the following four paperbacks from the early 70s to mid-80s.
The titles included "Gods From Outer Space" by Erich Von Daniken, "God and the Astronomers" by Robert Jastrow, "Flying Saucers - Serious Business" by Frank Edwards, and "Chariots of the Gods" also by Erich Von Daniken.
There were zero bids. I placed the opening bid of 99 cents plus $4.79 shipping & handling.
The next day, I received an email congratulating me that I was the proud owner of these books, and please send money.
I did. Via Paypal. The books arrived promptly, probably less than a week from when I originally placed the order. I had forgotten about them, so was surprised when I opened the nicely packed padded envelope. I laid them end to end to review them in person. Here is a photo of what I got for a little less than $6:

Now, the three books on the left were in great shape: no writing, few wrinkles of scuff marks, no writing inside. The final book on the far right was a disappointment. There was note writing right on the front cover, stains, creases, an lots of writing in pencil on the first inside text page when you open up the book.
Take a look at it here:

The book almost doesn't even make the grade as "Acceptable" according to Amazon's grading standards, and I still haven't decided if I'll even post it online. It may be a yard sale book at 25 cents sometime in the future. It might wind up being donated to a non-profit thrift store in my hometown.
Then, inside one of the books, I discovered a slip of paper, reading:

 "Thank you for your purchase, and we hope you visit our E-Bay store again. Positive feedback has been left for you, please leave positive feedback for us."

Now I do appreciate a genuine 'thank you' but this one seemed pretty artificial.
Second, I didn't buy it in their E-Bay Store, I bought it at one of their auctions. (Now I'm curious about what they have in their online store but they didn't list their website address. I probably would have browsed over to it if they'd given me a clue where to find them.)
Third, while I appreciate that they left positive feedback for me, I feel sort of pressured now to spend my time helping them look good to other shoppers. I didn't ask for positive feedback. They seem to be expecting it from me. Nowhere in the slip of paper does it mention that if I'm not positive about my purchase -- if I'm not a happy camper -- that I can email or call them to fix the problem. No email. No web address. No mailing address. No phone number. No way to get in touch with them, except for a general assumption that I'll be back on Ebay immediately to praise them. I do understand that I can log back onto MyEbay account and do all this.... but since they inserted this note in my purchase, why are they making it hard for me to find them again?
In general, they made me wonder: "Was this really a positive experience after all?"
Well... time to find out:
I began researching the going rates on these books, and the first three starting used book price ranged from $3-$4. Not bad. Not real good. But since they are in such good condition and I can sell one of them for $6-7, I believe that I can almost recoup my trial run investment.
In truth, I doubt if I will do any better than 'break even' on this deal. But no big deal. This was a test purchase and I learned some valuable lessons in the process.
I would not have paid more than 50 cents apiece for the first three books, and I'd have passed on the final one completely. I'd have only had then $1.50 tied up in three paperbacks, not $5.78 in four paperbacks. I would have had $4 dollars left to buy more books.
But this doesn't mean that buying used books on Ebay and reselling them at a higher price on Amazon is a bad idea. I feel it is just harder to find a real "steal" like you can at a thrift store, library fund-raising book sale, or an estate auction, where I've found stacks of books for as little as 10-25 cents that have sold for $10, $20, even $30 or more online.
And, this doesn't mean I won't take advantage of a good deal if I spot one on Ebay in the future, and I by no means wish to demean or disparage the seller. He or she did a really good job packing and shipping the books. But I do wish there had been more detailed information in the auction listing so I could have made a better informed choice.
Yes, I know, it is "buyer beware" out there and on Ebay you should ask lots of questions before placing a bid. But time is money. I had already spent nearly an hour searching out the books that looked promising to buy and sell, so writing an email and waiting for a reply only seemed to further complicate the process.
In my opinion, this was a good test, and know I have at least an inkling of how to search online at Ebay in the future for good deals to buy and then post used book titles online at Amazon Marketplace to get a nice return on investment.