I have some of their inks too (theirs is one of my favorite turquoises) and like them a lot. They don't say whether they are safe for fountain pens (on the packaging I have) but I have always suspected them to be ok as they are very transparent, but obviously you make your own decisions about that!
The first bottle I bought was from Joseph-Beth Booksellers in Lexington, KY and it was maybe around $10, and it holds a lot of ink (I am not sure how much, but the bottle is about the size of a Levenger bottle).
I also have the set from your link, and I like the inks a lot - there is one out of those 12 bottles I would not use in a FP because it has extremely fine metallic flakes in the ink, almost like those artists mica powders - but otherwise I like the colors. I bought mine from Paradise Pens around Christmas of 2005. They had it in their catalog for around $40 so your price is good.
Hope this helps - email me if you have any more specific questions about the set!

Marina.