2 channels.
Just check coupons out (with price alert and history). Best price?
Aliexpress
There’re some similar (or not) items on Aliexpress
You can use link bot to get even lower price:
Click here to search by yourself. Here are coupons that you can use.
Latest coupon code price check (UTC time):
Banggood
Banggood warehouse is located in China. There is one great coupon!
Link: Banggood product page
1. ($24.79): BGf2b910
just apply this code in your cart after clicking “Proceed to checkout”. Click to copy code and open shop.
Exclusive Allowance Coupons: https://bit.ly/3xWgD9k and https://couponsfromchina.com/short/i1u
There were country-specific coupon codes published on Couponsfromchina social channels and price alerts. Coupon price may vary by country, because there’re different VAT rates, shipping cost etc. There is a chance that some latest coupons are still working:
Old coupons (from the oldest to the newest): e2bcea, 502C6B, 847fc3, elec, BGMINIT1, bGhOnEy10, BGSMOFF, BGSONOFFT1, 13f142, BGSONOFF15, BGELIG0920, BgcLuBofErtA10, BGSONOFF16, BGAFF10OFF, BGSTHO15, BGCuponation10, BGHONEY2110, BGSHOM15, BGSHE15, 6GSGIT, ADMITAD2212, BGSmart6, MVC8SPRING, BG15Sonoff, Cuponation9, BG8ReviTrage, BG597de7, BG12MAY2023F, BGdd54b4
(sometimes old coupons work, so you can check them out (this site checks them on every price update))
Other warehouses/versions
This item is available in 3 another warehouse/versions!
1. China – SONOFF T1 3CH Wifi Smart Switch ($-3)
2. China – SONOFF T1 1CH Wifi Smart Switch ($-3)
3. Europe – SONOFF T1 2CH Wifi Smart Switch [EU] ($-3)
Price history and price alert
Check out price history chart (for all/most countries) for SONOFF T1 2CH Wifi Smart Switch. The lowest price was: $12.03.
Price records source(s): Gearbest, Banggood
Click on image to enlarge. 
You can set price alert (for Banggood and Aliexpress (only if product name will be the same as on Banggood and I will post it on social media though, so it’s more like Banggood price alert)).