Continuous current: 6A, Dimensions: 9.4x 21.5mm, BEC: no, MCU: EFM8BB2, Weight: 2.1g, Burst current: 10A, Voltage input: 2S LiPo, Item name: Bullet Series BLHELI – S 6A ESC.
Basically copy coupon, view price history or create e-mail price alert. 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. ($5.74): BGAFF10OFF
2. ($5.74): BgcLuBofErtA10
3. ($5.87): Parts8
this code has to be applied in your cart 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): TTxBG10, 2019SPEDM, bgssaff9, AFfbG10, BGVDay10%off, bGhOnEy10, BGdragonBoat, BgoFErTaSchInA10
(sometimes old coupons work, so you can check them out (this site checks them on every price update))
Price history and price alert
Here is price history (for all/most countries) for EMAX Bullet Series BLHeli-S 6A Brushless ESC. The lowest price was: $2.99.
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)).