I know this topic is for bargains, but it was a bargain that got me to waste money on this one:
"High Precision Ultra-low Power BMP280 Digital Barometric Pressure Sensor Board Module Swap I2C/SPI BMP280 BME280 3.3V Blue"
If you search for “BME280” on Aliexpress, this listing will show up also. And it looks considerable cheaper (€ 1,28 / piece) than other BME280 listings. That is because it isn’t a BME280, but a BMP280. This means no humidity measurements. The description doesn’t claim those measurements can be done, it is just the BME280 in the title that got me to waste money on them.
Even as BMP280, they are not very reliable. I ordered 5 of them. The pressure measurement reported by some of them is way too low, the temperature reading fluctuates a lot and the altitude meter is incorrect by about 100 meters.