Aliexpress
Here are coupons that you can use.
Other warehouses/versions
This item is available in 2 another warehouse/versions!
1. China – BlitzWolf BW-SS2 100W/50W RF 433MHz Smart Switch 1 Way (-3 USD)
2. Europe – BlitzWolf BW-SS2 100W/50W RF 433MHz Smart Switch 2 Way [EU] (-3 USD)
Latest coupon code price check (UTC time):
Banggood
Banggood warehouse is located in China. One coupon is available. Cool!
Link: Banggood product page
Coupon (7.19 USD): 10%ForNewBW
(CouponsFromChina.com tip: you should apply the coupon in your cart after clicking “Proceed to checkout”. Click to copy code and open shop)
Exclusive Allowance Coupons: https://bit.ly/3xWgD9k
Old coupons (from the oldest to the newest): BGBWSS2, BGSS21, 13f142, BG9NY, BGBWSS02, 2020CNY, BGVDay10%off, BGSAMH, bGhOnEy10, BGSM15, BGBWUU1, BGSMOFF, bgshOOp10, BGSAMRTH, BGBW152, BgcLuBofErtA10
(there’s a little possibility that old coupon will work)
Other warehouses/versions
This item is available in 2 another warehouse/versions!
1. China – BlitzWolf BW-SS2 100W/50W RF 433MHz Smart Switch 1 Way (-3 USD)
2. Europe – BlitzWolf BW-SS2 100W/50W RF 433MHz Smart Switch 2 Way [EU] (-3 USD)
Price history and price alert
Price history (for all/most countries) for BlitzWolf BW-SS2 100W/50W RF 433MHz Relay Module is here.
Price records source(s): Banggood
Click on image to enlarge. 
You can set price alert (for Banggood).