The Door entry project cost me £45.39 as show in the item breakdown below:
£14.90 Electric strike
£6.50 Raspberry Pi Zero (£4.00 + £2.50 delivery) £6.25 Philips SBCCS030/05 12V 200 mA Power Supply UK DC Mains Adapter £4.50 Micro USB Power Supply For Raspberry Pi Computer £3.69 USB 2.0 LAN Adapter to Ethernet RJ45 Network Cable 10/100Mbps Windows Linux Mac
£2.98 20 METERS OF 2 CORE FLAT BELL WIRE - 1 Amp Rating - LOW PRICE!! £2.39 UK NEW Micro SD 8GB 8G SDHC TF Flash Memory Card For Tablet PC Mobile Cell Phone
£1.97 RFID housing (electrical faceplate and matching slim box from B&Q £0.99 + £0.98) £1.88 Micro USB Host Cable Male to USB Female OTG Adapter Android Tablet PC & Phone £0.33 Raspberry Pi case (air tight food container purchased as a set of 3 from the Pound store)
I didn't include the price of the green + red LED, the network cable, the momentary push button, the 2 hot glue sticks required to glue the cabling around the door way, or my labour time. If you included my labour time at a cost of £10 per hour, I suspect it would have cost around £200 at least.