Hi Liz Sagara! The big ear variety is new to half moon bettas, and there are not many around yet which is why they are more expensive. It is difficult to find a quality big ear betta right now with nice body conformation and coloring, so the nicer big ears are very expensive.
If you are serious about breeding and are planning on selling bettas, then I'd start working on a big ear line because they are becoming popular and people are willing to pay extra for a nice specimen. If I wanted to make money selling bettas right now, I'd snatch up the best pure white big ear male and female betta I could find.
In general, Aquastar71 (the seller of the big ear female you posted) is one of the highest quality betta breeders I've found, so if you are looking for a breeding pair I'd keep and eye on his auctions. You can always request that a sibling male or female be shipped as well so you have a breeding pair.
I'm not familiar enough with giants to comment on them.