You're not wrong. To purchase ex-BUD fares, you have to ex-BUD, meaning, depart from Budapest. Paying for ex-BUD fares in North America should be easily doable, but forget about starting your trip here, you'll have to get yourself to Hungary on your own. However, you may only need a one-way ticket as you can end your trip in North America, assuming that you're travelling Eastwards/Southwards from Europe. Also, remember that you're limited in the continent of departure in terms of stop-overs, so you wouldn't see a lot of Europe/Middle-East.