The price of lithium batteries is mainly related to capacity. I wonder what voltage you purchased? Lithium batteries with the same amp hours are also voltage dependent;
In addition, the quality of lithium batteries also varies greatly. If lithium batteries are produced by regular domestic manufacturers, the quality is good, but. it is difficult to say that other small manufacturers' products are of good quality;
For reference only.
The rated voltage of the lithium iron phosphate battery is 3.2V. Mobile power supplies generally use 3.7V ternary or lithium cobalt oxide batteries. mobile needs to increase the voltage to 5V for output. If the voltage is low, the conversion efficiency will be low. The attached figure shows the charge and discharge curves of lithium iron and ternary batteries.