I got the Mi Band 6 when it was on sale for $25.
https://hekka.com/products/xiaomi-mi...cid=21k6_ovot&
Prior to that I had a Mi Band 3 for 3 years that I got for $12 when it was on sale.
The 6 adds SpO2 sensor and a color display, and needs to be charged once a week instead of once a month.
Easily the best value in the low end fitness trackers.