I've tried several times on different shops but some hotkeys are buying the items above the supposed item they are linked with.
For example, I tried buying Echo Sabre but end up with HotD. Tried buying a Demon Edge but bought an Ultimate Orb.
Tried Blink Dagger but bought a Ghost Scepter. Shadow Amulet hotkey buys a Morbid Mask.

PS: I did this in demo mode, not sure if it works fine in a real game.