Basically copy coupon, view price history or create e-mail price alert. Best price?
Aliexpress
There’re some similar (or not) items on Aliexpress
Click here to search by yourself. Here are coupons that you can use.
Latest price update (UTC time):
Standard Pass/Fail on-site test and alert function, Total amplitude accuracy <0.7 dB, Waterfall plot graphic / modulation signal quality analysis / audio demodulation / ect. multiple general and extended test functions., -160 dBm Displayed Average Noise Level (DANL), 1 Hz minimum resolution bandwidth (RBW), Multiple interfaces: USB Host / USB Device / LAN / earphone interface / HDMI, Adopt all-digital intermediate frequency technology, EMI pre-compliance test kit / optional EMC test software, 9-inch LCD / high resolution 1280X800 pixels, Phase noise -80 dBc/Hz @lGHz and offset at 10 kHz
Banggood
Banggood warehouse is located in China. There are no coupons for this product in Banggood.
Link: Banggood product page
Price: $-3
It looks like this item is out of stock in Banggood. If you found it then please send me the link. I will replace it.
Click here to search on Banggood!
Exclusive Allowance Coupons: https://bit.ly/3xWgD9k and https://couponsfromchina.com/short/5cd
Old coupons (from the oldest to the newest): BGfdd612, BGd5fb8d, BGb77532
(these codes were not working in latest coupon update, but you can check them out anyway)
Other warehouses/versions
This item is available in 1 another warehouse/version!
1. China – OWON XSA805 9kHz-500MHz Spectrum Analyzer ($-3)
Price history and price alert
Price history (for all/most countries) for OWON XSA815TG 9kHz-1.5GHz Spectrum Analyzer is here.
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)).