Oh, buddy...what's to be said. You paid some schooling money, can happen anytime, anywhere. There are some basic rules though (I repeat myself from other topics):
1) Check the profile thoroughly. Compare the photos with the text. Let your life-experience lead you.
2) Model-like girls are not typically on sites like these. That should ring the bells.
3) Read BETWEEN the lines. Nobody can hide everything.
4) Talk on Skype, insist on Video-calls. Try to be objective, just as in everyday's life.
5) DON'T SEND CASH. Send a non-refundable e-ticket if you are to meet somewhere else.
6) It is not the last truth, that much younger women want to cheat older men in generally. There ARE women who look rather for older partner. But there must be a logical thinking, also there. Anyways 20+ years is always to be double-checked anyways. Not only because of a potential scam, but also because of the future. A 50 y/o woman might maybe be satisfied with a 70 y/o man who is FIT, but with a 80 y/o ???
And no, don't lose trust in the Russian/Ukrainian etc people. They are not cheating by default.