If you're looking for a good phone under $150, Motorola's G4 Play is probably one of the best options. You get a Snapdragon 410 CPU, 2GB of RAM, expandable storage, a removable battery, and Android 6.0 Marshmallow (with Motorola promising Nougat soon). This is also one of the few phones in this price range that supports GSM and CDMA, meaning it works with all US carriers.
Now you can snag a G4 Play on Amazon for $20 shy of the $150 MSRP. This is not the Prime Exclusive model with ads, this is a completely unmodified device.
Only the black color is discounted, the white model is still $150. Both models have Prime shipping available.
Keep in mind that this is a different product from the similarly-named G4 Plus and G4, which are both priced above the G4 Play. I wish Motorola would have stuck with making one phone for high-end, mid-range, and low-end - it was much simpler.