I see on Lazada.com.th(an online shopping site for Thailand) a list of power banks:P 30,000mAh, 40,000mAh and 50,000mAh for from $6, $9 and $12! I'm will to buy the 50,000 PB, so how can I tell if I'm wasting my money or getting an unbelievable value? Lazada is a good value web site, BTW.
Also...