This is a question we see quite a lot, and the answer is quite simple. As with eBay, you will find a lot of different sellers on these very popular platform. Everyone from small mum and dad sellers, right through to big business sellers.
You have to compare apples with apples. If you are looking at drop shipping prices up against sellers who are buying in large volume and selling on thin margins, then you have zero chance of finding a price that will match them, let alone one that will allow you to compete.
If you have the money available to buy in a volume that will allow you to get the big wholesale volume discount, then you can compete against most sellers on Amazon and eBay. That said, most of us don't have the cash flow available to us, so drop shipping is an avenue that we exploit.
To exploit drop shipping effectively, you need to find product markets that will allow you to do so.