Seeing two different levels depending on whether you go westbound (DL+KE), or eastbound. Difficult to find the westbound option from the east coast (there's better availability from the west coast like SEA). Not sure how OP is coming up with 260K (none of the levels below add up to that). Fare construction would be helpful. 2 CSV1350's would be 270K. 330K would be two CSXR1650's.

lowest one-way levels
CSV1000 (westbound, 90-day AP)
CSV1350 (eastbound, 90-day AP)

lowest RT levels (each way)
CSXR1650 (60-day AP)
CSLR2300 (21-day AP)