Prop adapter shaft thread: M5, KV: 1750KV / 2150KV / 2400KV / 2700KV, Rotor: N52H arc Magnet, Weight: 32g with 16cm SR wires, Wire AWG: 20#, 16cm Length, Configuration: 12N14P, Bolt pattern: M3(16X19mm), Base case: AI 7075, Bell cap: AI 7075, Item name: Returner R6 2207 Brushless Motor, No. of cells(Lipo): 4-5S, Stator: 0.15mm Nippon steel silicon steel, Shaft: Titanium Alloy hollow shaft, Bearings: Japanese NMB 9X4X4.
Price history, coupons and price alert are available on this page. Let’s see what best price is ATM.
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. ($24.83): BG28RC
2. ($31.73): Parts8
you should apply the coupon 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): BGfpvmagazine3, 502C6B, 0e7f33, FBCOUPON1, 935D63, BGAFF10OFF, BGCuponation10, BGDAVIS, BGHONEY2110, 28RC
(I don’t think these’re gonna work, but you can try ’em out anyway)
Price history and price alert
Here is price history (for all/most countries) for BrotherHobby Returner R6 Rainbow 2207 4-5S RC Motor. The lowest price was: $20.99.
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)).