You can create price alert here, copy coupons and view price history. Best price?
Aliexpress
There’re some similar (or not) items on Aliexpress
| Image | Product (link) | Price | Coupons |
|---|---|---|---|
 |
D75mm Neodymium magnet super powerful hole Double-sided salvage fishing magnet 300kg Circular Ring hook permanent holder Steel | $11.58 | – |
Click here to search by yourself. Here are coupons that you can use.
Latest price update (UTC time):
Color: Silver, Diameter: 75mm, Weight: 750G, Max vertical pull: 300KG
Banggood
Banggood warehouse is located in China.
Link: Banggood product page
1. ($29.50): BGherra
2. ($31.24): BGAFF10OFF
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/5cd
Old coupons (from the oldest to the newest): BG2199, elec, 9ca9bc, a33514, BGMPJ16, BG219, TS15prime, BGCITYADS2019, AFfbG10, BG2020NS, 0e7f33, BgcLuBofErtA10
(I don’t think these’re gonna work, but you can try ’em out anyway)
Price history and price alert
Price history (for all/most countries) for 300kg D75mm Neodymium Magnet is here.
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)).