名牌货打折, 其实是一种比安全且高效的操作

at its heart, it's actually a great example of trend following, (surprise!), that,

once a 名牌, will be 名牌 again,

but tactically, it's application of another trading rule, short term mean reversing. That extreme deviation will tend to correct itself.

2 conditions for such opereation, you have to be fairly sure 1, it's a 名牌, and short term trigger event is not as substantial as the market had believed, 2, 打折 has been substantial enough to offer enough margin for safety,

the last question left actually, when and how much to build positions? One way is do it mechanically, average down from every certain step, the other is try to access the market sentiment (or craziness), and try to use short term charts to be more measured in selecting entry points and sizes.