How profitable is running a 3PL business? Do you know what net profit % most would operate? Who has had experience working for a logistics company?

I have made headway doing fulfilment for a few E-COMMERCE brands in Australia at a smaller scale and it is definitely profitable on a small scale. I want to get an understanding of the ins and outs from someone that has been in the industry and knows what net profit % most 3pl providers generate.