I paid 1800 in the east bay. Another shop quoted me 2100 so I would say its a bit high but in the ball park. If it was me I would regear to 5.38 in the event you go to 35s down the line.Your LJ was under-geared from the factory. For 31" stock tires, Jeep should have put in 4.56 or 4.88 gears instead of the 4.10's they did. The 42RLE has an overdrive ratio of 0.69, which is pretty tall compared to the top gear ratio of the manuals.
$2400 is ridiculous. Total to re-gear should be around $1500 for both axles. That number does depend on your region, but I couldn't imagine that it would be $2400 (especially per axle!). If I was in your position, I would probably put 5.38 Revolution gears in. If you ever decide to go to 35's, 5.38 would be what you want. 5.38 with 33's wouldn't be terrible either.
35s just look so good on ljs