Hardware versus labour: the split your quote should always show
The most common way people overpay is by accepting a single bundled number. A quote that says a smart lock 'supplied and installed' for one lump sum hides the markup on the hardware, which in the UAE can be substantial — the same lock model can cost noticeably more through an installer's supply price than it would if you bought it yourself online or from an electronics retailer in Dubai or Sharjah.
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.