$17.99 – Enclosure Material: Fire-retardant ABS V0, Security Mechanism: WPA-PSK/WPA2-PSK, Gang: 2, Color: White, Max Current: 15A(total) /10A(1 gang), Humidity: 5%-95%RH / Non-condensing, Frequency: 802.11 b/g/n, Operating Temperature: -10ºC-40ºC, Product Dimensions: 54*49*24mm, Power Supply: 100-240V AC, Max Power: 3300W(total) / 2200W(1 gang).
According to my DB the lowest price is $17.99 for SONOFF DUALR3 Dual Relay Module Switch (in Banggood). Price history, coupons and price alert are available on this page. Do you want to know what the best price is?
Latest coupon and price update (UTC):
Banggood ($17.99)
Banggood warehouse is located in China. I don’t think there is an active coupon right now – at least in my database. Is it a low price? Hmmm, price is higher than average (which is $11.94 right now), so better set price alert down below…
Link: Banggood product page
Price: $17.99
Additional Banggood coupons: first page and second page
Old coupons (from the oldest to the newest): BGDUALR3, BGDUALR313, 13f142, BG36c08a, BGee1672, BG619c1a, 6GSGIT, ADMITAD2212, BGSmart6, 8Couponsde, MVC8SPRING, 8wEbgaInS5, pROMo8cuPoN, BGJUNEGSG9, BG15Sonoff, BG8ReviTrage, Cuponation9, 9OFFSUMMER, BG32140d
(you can check these old coupons out, but these probably won’t work)
Other warehouses/versions
This item is available in 1 another warehouse/version!
1. Europe – SONOFF DUALR3 Dual Relay Module Switch [EU] ($-3)
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.
Price history and price alert
Here is price history (for all/most countries) for SONOFF DUALR3 Dual Relay Module Switch. The lowest price was: $9.99.
Price records source(s): 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)).
. There are no coupons for this product in Banggood. I don’t want to misguide you about the price. I don’t know if it’s good, because I don’t have enough records in my database…