for 1C robot, 2 pieces in the package.
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 price update (UTC time):
Banggood
Banggood warehouse is located in China.
Link: Banggood product page
1. ($10.79): BGSTHO15
2. ($10.99): 13f142
put item in your cart and apply coupon code there after clicking “Proceed to checkout”. Click to copy code and open shop.
Additional Banggood coupons: first page and second page
Old coupons (from the oldest to the newest): BGSAMH, bGhOnEy10, BGSM15, BGSMOFF, bgshOOp10, BGSAMRTH, BgcLuBofErtA10, BG15SH12
(probably won’t work, but you can try them out)
Price history and price alert
Check out price history chart (for all/most countries) for Xiaomi Mijia 2Pcs Edge Brush for 1C Vacuum Cleaner. The lowest price was: $9.43.
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)).