Yes you did read that correctly. That Ali Express $9 box dye has the same chemicals as the salon — minus the training, the second pair of hands, and the ability to see the back of your own head.
The results speak for themselves: stripey banding, orange patches, stained foreheads, a bathroom that smells for two days. And if it goes really wrong, a color correction costs $300+ — more than the salon you were avoiding.
Box dye only works reliably in skilled hands.
And let's be honest, me and you, If we had skilled hands, we'd be charging for touch-ups, not paying for them.