Some Arduino components seem ridiculously cheap My project is an Arduino-based device, packed into a box.

It will need to use Speed, Latitude, Longitude and Altitude data to log hills it detects on to an SD. On the press of a button, it will need to upload the hill data to the server via Wi-Fi.

I need the following items:


GPS Module + Antenna
WiFi Module
SD Module
Altimeter
microSD Card
Inline switch for my battery pack


The cost? Well on the Pi Hut it was £120 or so:


  GPS =
  https://thepihut.com/products/sim808-gps-gprs-gsm-shield-for-arduino =
  £42
  
  WiFi =
  https://thepihut.com/products/wifi-shield-v3-for-arduino-rpsma-802-11b-g-n
  = £54
  
  SD = https://thepihut.com/products/microsd-card-module-for-arduino =
  £6
  
  microSD Card = https://thepihut.com/products/blank-micro-sd-cards
  (4GB) = £5
  
  Altimeter =
  https://thepihut.com/products/adafruit-bmp280-i2c-or-spi-barometric-pressure-altitude-sensor
  = £10
  
  Switch =
  https://thepihut.com/products/adafruit-in-line-power-switch-for-2-1mm-barrel-jack
  = £2.50


On Bang Good (a really cheap online shop I discovered) it was more like £30:


  GPS = 
  https://www.banggood.com/GPS-UBLOX-NEO-7N-Satellite-Positioning-Module-For-Arduino-51MCU-STM32-p-1203610.html?rmmds=cart_middle_products&amp;cur_warehouse=CN
  = £10.54
  
  GPS Antenna = 
  https://www.banggood.com/GPS-Active-Ceramic-Antenna-IPX-IPEX-Interface-For-GPS-Module-p-1203537.html?rmmds=cart_middle_products&amp;cur_warehouse=CN 
  = £2.11
  
  WiFi = https://www.banggood.com/Upgraded-Version-1M-Flash-ESP8266-ESP-01-WIFI-Transceiver-Wireless-Module-p-979509.html?rmmds=cart_middle_products
  = £2.53
  
  SD = https://www.banggood.com/Micro-SD-TF-Card-Memory-Shield-Module-SPI-Mciro-SD-Adapter-For-Arduino-p-919914.html?rmmds=cart_middle_products&amp;cur_warehouse=CN
  = £1.02
  
  microSD Card = https://www.banggood.com/4GB-MicroSD-Card-with-Card-Reader-for-RC-FPV-Camera-Quadcopter-p-1050069.html?rmmds=cart_middle_products&amp;cur_warehouse=CN
  = £3.96
  
  Altimeter = https://www.banggood.com/MPL3115A2-IIC-I2C-Intelligent-Temperature-Pressure-Altitude-Sensor-V2_0-For-Arduino-p-1198222.html?rmmds=cart_middle_products
  = £5.16
  
  Switch = https://thepihut.com/products/adafruit-in-line-power-switch-for-2-1mm-barrel-jack
  
  = £2.50 (From Pi Hut, though)


I'm suspicious. I might be inexperienced, and this may be a bad question, but is the cheaper option lower in quality? Is the expensive one over the top? The cheap version really seems to good to be true.
The cheaper option is not always lower in quality. You can find items for sale on Amazon, Ebay and Aliexpress that all have the same "seller name" and a identical picture of the item. The price is usually 5 to 10 times higher on Amazon than Ebay. Aliexpress is usually the cheapest.

During the past year, I've ordered over 100 Arduino related sensors/modules from Ebay and Aliexpress. Four from Ebay and one from Aliexpress were defective. I got a refund for all five items.

If you are going to buy the cheaper products, it's a good idea to order more than you need in case one is defective.

Some items should not be sold at any price. For example, I purchased a DHT11 temperature and humidity sensor when I first started with Arduinos. It's an inaccurate piece of garbage, and that's exactly where it went.