$37.59 – 100A PWM Solar Controller (Banggood, Aliexpress: Max. PV input power: 750W(12V) / 1500W(24V), Rated voltage: 12/24V, , Max. PV voltage: 50V, Rated current: 40/50/60/100A (the best price with coupon)).
100A PWM Solar Controller is for $37.59 (in Banggood). Just check coupons out (with price alert and history). Let’s see what best price is ATM.
Latest coupon and price update (UTC):
Banggood ($37.59)
Banggood warehouse is located in China. So I have checked for active coupons (all category coupons and old ones), but there was no working coupon in Banggood. Price? Maybe there’re no more promotions for this item, because current price is higher than average (which is equal $20.53)
Link: Banggood product page
Price: $37.59
Exclusive Allowance Coupons: https://bit.ly/3xWgD9k and https://couponsfromchina.com/short/5cd
Old coupons (from the oldest to the newest): BG4b5920, BGc03ecf, BGfcfd82, 00c906, BG00c906, ADMITAD2212, 2022ACTIESNL, Tabby20, 2203ActiesNL, tRaDetRaCKeR, 8wEbgaInS5, BG08bdfc, pROMo8cuPoN, BGb305f9, BGRSUNLCD, BG6d2f05, BG1eb57a, BGHUXC060, BG37b1ad, BG4de751, BG7e07bc, BG0b9613, BG589884, BG8OFFCOUPON, TTBLACK5, BG589b2e, BG1d613b, BGET12, BG350285, BG5ef911, BGc9f4ac, BG68ab79, BGe4341d, BGa78dae, BGa61103, BGdb01a1, BG3bca8b, BGET10, BG8FORMULAMX
(these coupons are old, so probably won’t work)
Aliexpress
There’re some similar (or not) items on Aliexpress
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 100A PWM Solar Controller. The lowest price was: $17.99.
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)).