Let's see....Originally Posted by PhoenixAsh
"In the hearts of the damned / Lies the scourge of the land"
The scourge of the land, from an initial reading, could arguably be any of the following: Sephiroth, Jenova, Hojo, Meteor, the original crater, Black Materia, Rufus, President Shinra, Shinra (the company), its employees, Midgar, Mako reactors, WEAPON, or humanity in general. Or even something else. I'll narrow this down as I consider the rest of the riddle.
"In an orb and a bird / Can a new hope be heard"
The most apparent connotation here is Phoenix materia, which incorporates the concepts of orb, bird, and (new) hope. However, Fort Condor has already been dismissed as an answer, so I'll reconsider the line's meaning. Bird, taken literally, could possibly refer to the following: anything Chocobo related, or it could refer to the fight for 10 Phoenix downs with the birds on the way to North Corel. I don't think bird is meant literally, however, and this will be reflected in my final answer.
"If the two are put together, / Then the price has been paid. / So the question I ask / Is just where was the trade?"
Price can, it seems, have a literal or metaphorical meaning here. I think the riddle ultimately hinges on, however, determining just what is being referred to by "trade."
I fear this is off, but I'm nevertheless going to guess that the location referred to is the Water Altar under the Forgotten Capital/City of the Ancients. Hearts of the damned/scourge of the land could refer to Seph, with additional emphasis possibly added to Jenova. The orb could be Holy materia; the bird Aeris' prayer (flying up?), and the potential effects of Holy the new hope. If Seph and Aeris are together at the Water Altar, we all know what happens. This then would be the trade, and the price paid: a prayer for Holy, at the expense of Aeris' life.