I suspect it is just supply and demand. People have been waiting for the gates to open and a year's worth of interest is now being compressed into half a year, and only 2 of 3 airlines are flying there from the US.
June is VERY high right now, July is getting there, August is beginning to see some reasonable prices. Sept goes back up (see below).
it makes a huge difference exactly which day you fly, and which day you check prices.
Right now, RDU-BON RT for 7 days on Delta, Saturday to Saturday, is running $756 to $1466 in June, depending on which Saturday you choose. Weds-Weds trips are $596-$685. These are the lowest prices, and may not be the most convenient flights.
In July, Sat-Sat is $1201 to $2086, and Weds-Weds is $566-$641.
In Aug, Sat-Sat is $661-$881 and Weds-Weds is $566-$2247.
In Sept Sat-Sat is $1411-1776 and Delta has stopped Weds flights, which pushes up the Sat prices.
You'll find American prices better than Delta, pretty much across the board.