Hi all,
I noticed this post a bit too late, but I hope this information will still help you out.
It are indeed Dutch (handmade and hand painted) antique tiles, made at the end of the 17th century (c. 1680) and basically at the end of the Dutch Golden Age. It looks like some tiles might have been made in the same factory, as they show strong similarities in the way the sea creatures, the sea and corner patterns were painted. Some tiles are decorated with so called 'ox-head' corner patterns and the one with the 'dots' is known as a 'spider' corner pattern.
Yes, you can indeed buy Delft tiles on eBay for a rather low price, but do note that the overall condition, the quality of the painting, the depicted image and the age of the tile are of a big influence on the value. Many of the tiles on eBay have old restorations, are badly damaged or are simply too common to be worth a lot. The rare tiles that occasionally come by are not sold cheap.
The tiles you bought seem to be in a pretty good condition, although the top left tile might have been broken. The depicted sea creatures are very entertaining to watch and most definately worth collecting. In my opinion, you made a great purchase (a bargain to be honest 
)!
The Philadelphia Museum of Art has a great collection of antique Dutch tiles. I believe there was an exhibition quite recently, but not sure if there is anything running at the moment. Some of the tiles they own can be found on their website: http://www.philamuseum.org
If you have any questions, do not hesitate to get in touch. Good luck!
Durk
(the owner of the previously mentioned webshop)
Durk, thank you so so much for that information! Exactly what I was looking for.
I picked up the tiles earlier today. I love them. (as if I needed something else to collect!)
Worth every penny of $150 USD to me.
A few do have some obvious damage, but I actually think it adds to the story and look. (obviously hurts the value though)
Four of them are framed.
So you believe these are definitely late 17th century tiles?
I'm sure I will have more questions. Would you mind if I emailed or messaged you?
Here are some quick photos of each of the 12 tiles for anyone who is interested.
