Yes, it does, for a given voltage and current rating.
mAH does denote the amout of power the battery holds. It is basically represents how much current can be drawn in 1 Hour of time. In other words, how long the 100% recharged battery lasts when drained at 1 milli AMP.
Typically, a quadcore mobile, when not used (screen switched off and not playing any music) would draw power as low as 25mA. A 1000mAh battery would last for 40hours on such mobile, when not used actively (1000mAh = 25mA x 40 hours).h
The Higher the mAH rating, the more is the duration of the battery with a single recharge.
Batteries of mAH rating of 900mAh to 3500mAh are not uncommon. A reasonable power banks typically hold anywhere between 5000mAh to 25000mAh.
The manufacturing cost of good quality Li-ion or Li-po battery would cost ₹5 per 100mAh (or $0.1 per 100mAh). It would approximately cost ₹1000 for 20,000mAh battery.
Companies like Xiomi hardly make money with its ₹999. 10400mAh power bank.