Hardware versus labour: the split your quote should always show
Ask every vendor to split the quote into device cost and installation labour. Install-only pricing for most single devices — a lock, a doorbell, a thermostat — typically sits in the AED 200–450 band. If the bundled quote is far above device retail plus that band, you are paying a convenience premium and should at least know you are paying it. Sometimes the premium is worth it: the installer warranties the whole job, sources a model they know works with UAE door profiles and AC systems, and will not blame your hardware if something fails.
The reverse trap also exists. Buying your own device to save money and then discovering it does not fit — a smart lock that will not mount on a UAE-standard aluminium villa door, a thermostat built for a wiring standard your AC does not use — turns a saving into a return-shipping exercise. The sensible middle path is to choose the device yourself but send the exact model to the installer before purchase and ask them to confirm compatibility in writing, even just over chat.