Supplier buying my listing?

I’ll preface this by saying im no expert in this field. It’s more of a hobby than a side hustle/job. I’m near the end of my run because I just don’t think I can be successful in FBA.

Normally I average around 80% acos for PPC. It’s not profitable. I’ve placed about 3 orders of 1000 units. My supplier is Alibaba (I know). The strangest thing happens when I get low to 50ish units. My acos drops to like 10-15% and all of a sudden I’m profitable.

Just when I’m about to throw in the towel, I’m encouraged to place another inventory order. Could my supplier be trying to ‘trick me’ into buying more units?