You can actually see some of the cost cutting just in the visible PCB design. The big component that is missing is for signal conditioning. You’ll find it on most Ethernet adapter like this. But not on this one! 

You can see the 4 Ethernet data traces, instead, pass through 4 capacitors that are much cheaper. Costs savings that result in lower quality data transmission. 
Also notable is that this PCB was designed to support either config. That saves $ when you can use the same PCB for both the lowest cost product and one that sells for a bit more.