Seatgeek also spoke to James Kimball of MMA Mania who shared the following thoughts on the reason for the difference in price:
The real interest of this event doesn’t revolve around the UFC’s debut in Boston, or even the main event featuring a rematch between Frankie Edgar and B.J. Penn for the lightweight title, which we’ll touch on in a moment. The real interest, the reason so many extra eyes are tuned in to the lead up to UFC 118 is the heavyweight fight between aging boxer James “Lights Out” Toney and MMA legend Randy “The Natural” Couture. While the particular combatants in this match up are very appealing considering both of their accomplishments in their respective sports, it is the idea of MMA vs. Boxing, or UFC vs. Boxing as Dana White and Zuffa’s marketing team has labeled the showdown, that truly grasps the attention of fight fans.
I disagree with James that the bump isn't coming from the Boston debut. It is certainly due in large part to Toney/Couture but the first trip of the UFC to a major market almost always does big sales. There also is the fact that the 119 tickets are cheaper because a card headlined by Frank Mir (lost 2 of his last 3 fight) vs. Mirko "Cro Cop" Filipovic (who has not had a ton of Octagon success) is not going to sell the same as a world title rematch supported by a bout between two combat sports legends.