It could be worth it in the end. some people spend more than that on a lesser sized salvage axle and then spend more simply replacing stock pieces. You will still have a stranger center section, not that its needed, and alloy shafts. You might check to see what axles they are because they might be warranty parts, but you might need a receipt too.
Things you should consider though, will the axle fit your app manily width and bolt pattern., you will have to re-gear you front or the 9" to match, you will need to fab the axle to your app, you will probably need a new driveshaft. I would assume this 9" has a spool or some type of locker, this could be a bonus or you will need to buy something different. If the bolt pattern is differnt or the axles are drilled for multi patterns, you might be ok if you have to order new axles, or you will need adpaters or wheels.