If these vapes are disposable, wouldn't it be cheaper for the manufacturers to use non-rechageable battery technologies like the many ones on AA(A) batteries?
Consumers are paying upwards of $20 for vapes that last less than a week with heavy use, or about 2 weeks with low/average use, so I don't think a dollar saved on batteries is really as much of a concern as "why should I buy your vape vs one of the 5 dozen competitors'"?