The unlocked Nokia 3.1 is currently available for new all-time low prices at B&H Photo Video and Best Buy. Technically, the latter retailer is certainly the way to go if you want to maximize your savings, although you'll have to open a new AT&T account or add a line of service to an existing one to get the phone in exchange for a measly $89.99.
Alternatively, you can purchase it from B&H with absolutely no strings attached and spend $119.99 instead of a list price of around 160 bucks. Afterwards, you can take the dual-SIM Nokia 3.1 to whatever GSM service provider you want, including AT&T, T-Mobile, and smaller prepaid operators. It's also worth pointing out that Best Buy is only selling this in black, while B&H Photo Video has the blue/copper model in stock, listing two other flavors as "discontinued", which suggests we might be looking at clearance sales here.
After all, both a Nokia 3.1 Plus and 3.2 are around, although the former is exclusively available on Cricket Wireless, with the latter unlikely to ever see daylight stateside. In terms of sub-$150 competition, the Nokia 3.1 arguably looks better than the likes of the Moto E5 Play, with a slightly more modern 2:1 display, decent 2,990 mAh battery, an octa-core processor, 2GB RAM, 13MP rear-facing camera, and above all, Android 9.0 Pie software right around the corner. Bottom line, this is definitely a good enough phone at an unbeatable price.