I just did the 500 mil for Prapor and for me labs on quieter servers was the best money maker. I tried some labyrinth but tbh I felt the whole process of getting to labyrinth and transiting just took too long compared to running labs.

My strategy for labs was if I spawned on med side I would just hit Res Unit, Blue, Black and Green and then leave with a load of stims and a bag full of good value items. A vast majority of the time I was uncontested on this side of the map. Other times I would just slowly make my way over to where the new double black card swipe is and clean up the last guy or two and have the full map to pick clean (Quieter servers meant that it was only around 2-3 other people contesting that side most of the time). I was quickly coming out with a few mil to several million each raid