According to my DB the lowest price is 11.99 USD for 3.5CH Infrared RC (in Banggood). Price history, coupons and price alert are available on this page. You probably want to know what is the best price?
Latest coupon and price update (UTC):
Banggood (11.99 USD)
Banggood warehouse is located in China. Hmmm… There is no active coupon in Banggood at this moment. Price? It looks like it’s a good price (lower than average (12.71 USD)).
Link: Banggood product page
Price: 11.99 USD
Old coupons (from the oldest to the newest): BGQS5010, BGQS50101, BGToys8, BGMatt2022, BG20c79f, BG589b2e
(probably won’t work, but you can try them out)
Aliexpress
Click here… to search for QS5010 3.5CH Infrared RC Helicopter RTF on Aliexpress
Here are coupons that you can use.
Price history and price alert
Here is price history (for all/most countries) for QS5010 3.5CH Infrared RC Helicopter RTF.
Price records source(s): Banggood
Click on image to enlarge. 
You can set price alert (for Banggood).