Kwikset is still the least expensive, but also a tier down in quality from Schlage or Yale.
However, because of the zigbee hub inside some echo devices, we are starting to see many more zigbee devices being designed. And locks is one of the categories that the echo supports.
Also, Xioami has introduced their first smart lock, which is a very fancy one and won’t be what you want. But if that sells well, they might bring out a basic model in the future as well.
So my guess is that within the next year we will see multiple new zigbee locks introduced at a lower price point. I know that doesn’t help you now, but I just wanted to mention it in case you wanted to stick with dumb locks for now until there is more choice in the future.