I would guess that 500 trees is optimistic. I would say it would be more like 2-300 a day. With a dibble bar you may be able to get 500 in a day, but your survival rate will be much higher if you were to use a shovel. The issue with a dibble bar is that you are going to get an air pocket around the roots when you close the hole up, and all the soil is compacted around the roots. With a shovel you can make a wider or deeper hole, to fit the roots in properly and firm the soil down around the roots to make sure there are no voids of soil to root contact. The larger hole also makes it easier for the root system to grow the first year and to take up moisture.
So.... you either put a lot in the ground and hope the laws of averages comes out on your side, or get less in the ground knowing that you are giving them more of a chance to survive. I have planted with both methods and have seen a big increase of survival rates when planting with a shovel.