This seems similar to the WeChat plane ticket (and train ticket) feature, where everything is actually outsourced to another agency.

I haven't tried Alipay's version yet, but the WeChat one has always worked out fairly well the times I've used it. Like OP, I found prices that were significantly cheaper than Ctrip/Elong in a few cases (~100-150CNY on PEK-SHA, for instance). Plus, they occasionally send out various nice promo codes ("get 20RMB off your next ticket!"). Tickets weren't issued immediately but they always came through in time for the flight—occasionally just in time—and at the promised price. I'm pretty sure they're essentially hedging ticket prices or something behind the scenes here: when the WeChat tickets were the same price as pretty much everyone else, issuance was instant; the deepest discounts were the cases that led to tickets being issued hours before the flight.

When one of the CA flights I bought ended up cancelled, I called them up and they sorted it out and got me on a different flight in less than five minutes. I was a bit dubious, but the MU people found the new reservation without a problem. The only downside is that I'm 99% certain there's no English-speaking help desk or on-site staff like Ctrip has.