I hate to say it but it's not $3k. By my crude maths that front diff will owe you about $5150 in AUD. Then you still need to change the front panhard mount, pull out the old diff, remove the knuckles & brakes and refitt it all - or you need to allow to pay someone to do it. Heck even add another $20 in fluid.
You say you're bring 2 diffs - so is that a matching rear? If so by my crude math the $2682 (USD) will probably end up costing $4260.
0. Plus again yo need to change the panhard mount, remove the diff & brakes and refit - or pay someone to do it. Plus another $20 in fluid.
So now you are at $9450 AUD, AND you've still got all the labour I mentioned.
I don't want to rain on your parade, but you need to be a little more realistic in your pricing.
Edit: dang just beaten to the post