Although I know it is not possible to know the Google Adwords budget of a site without having its account details, any one has any tool or knowledge to share with which it is anyway possible to get an idea?
spyfu.com claims to, but when I've looked at sites I already know something about, the results look wildly inaccurate.
As Openeye said, there isn't a way, unless you can hack into their account or have a friend at Google who could look it up. Besides, what good is it going to do you?