The web site is telling you the the jailbreak is for iOS 4.3 and not for iOS 4.3.1, the dev team will go with web site that ask for money in order to jailbreak your iOS device.
I have jailbreak my iPhone 4 on iOS 4.3.1 but cydia is not ready for it and the iPhone get stuck so I had to downgrade...
If You save your SHSH file with Cydia you can use Tinyumbrella to to see if you save the files and to retrieve the files from Cydia and resotre to IOS4.1 then JB and Unlock.