$7.99 – Racerstar SG90 9g Micro Plastic Gear Analog RC Servo (Banggood, Aliexpress: Brand: Racerstar, Stall Torque: 1.2kg/cm / 16.66oz/in(4.8V); 1.6 kg/cm / 22.21oz/in (6.0V), Dead Band Width: 7us, Product: SG90 9g Analog Servo, Operating Voltage: 3.0V-7.2V, Weight: about 9g, Temperature Range: -30℃~60℃, Connector Wire Length: 245mm, Size: 3.2x 3x 1.2cm, Operating Speed (4.8V no load): 0.12sec/60 degrees, Application: For RC Helicopter / RC Airplane (the best price with coupon)).
According to my DB the lowest price is $7.99 for Racerstar SG90 9g Micro Plastic Gear Analog RC Servo (in Banggood). Price history, coupons and price alert are available on this page. You probably want to know what is the best price?
Latest price update (UTC time):
Banggood ($7.99)
Banggood warehouse is located in China. I can’t find any active coupons for this product in Banggood. You probably want to know if this is a good price. Well, this price is higher than average price ($7.06)
Link: Banggood product page
Price: $7.99
Exclusive Allowance Coupons: https://bit.ly/3xWgD9k and https://couponsfromchina.com/short/i1u
Old coupons (from the oldest to the newest): BGToys8, BGMatt2022, BG25d4e7, BG589b2e
(I don’t think these’re gonna work, but you can try ’em out anyway)
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.
Price history and price alert
Here is price history (for all/most countries) for Racerstar SG90 9g Micro Plastic Gear Analog RC Servo. The lowest price was: $4.99.
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)).