That's a pretty typical price for Rubi axles. Regearing your current axles and installing air lockers will probably cost you around the same amount. Realistically though you don't want to put a locker in your D35 and the upgrade to the D44 in the rear is a big improvement. Find out exactly what "everything included" means. Compressors, ebrake cables, maybe driveshafts, etc.? Faced with only those two choices I'd say get the Rubicon axles, although overall there may be better ways to spend $3000 on axles.
Axle swaps aren't hard. You're mostly just unbolting old stuff and bolting up the new axle. First time I did one took me a day for one axle although that was by myself.
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