I have that Su30KN, and it is the best Su that Gaincorp have made so far. And I have almost a dozen different ones. Got mine about a year ago from a seller in China, and it was about $120 with shipping. But relatively hard to come by at the time, and a great looking scheme.
However, Gaincorp need to pack their models better, as the styrofoam cradle that they use just doesn't give the model enough support.It can work loose during shipping, and knock bits and pieces off the model. A simple glue fix, but still.
As Gouchy has said the Flying Mule will be carrying this Su30KN, and the Su47 in the very near future, for substantially less than these were selling for not that long ago.
In regards to the 4 pack of Flankers. It also has the Su34, a side by side, two seater. Much like the F-111. These were pretty rare, and hard to find, and I was fortunate to get all three of them from a seller in China who didn't realize what a hard to find model he had. He had a few of these for sale, and the response was pretty strong, and he kept raising the price, but they kept selling. These were apparently selling for $200 when they showed up rarely on Ebay. Pretty sure they wouldn't fetch that price now, but these Su34's are still pretty hard to find.
Might be worth getting the 4 pack just for the Su34.
Gaincorp are a unique, and kind of quirky company. Based in China, and with no real distribution to the West.They make lots of different Su27's and variants. Gear down only option, which I am not a fan of. However, I do like my Gaincorp models. Not the absolute best quality, but pretty good, and they are a different kind of company.
I would definitely recommend the Su30KN.
http://www.flyingmule.com/products/GC-WA72022