You don't say if that is price each, or price for a pair. $40 for one of those TBS antennas is a rip-off. I have several, and they have stood up to some serious abuse, but they are far from the best from a signal quality perspective. You should try some VAS minion antennas.
https://www.readymaderc.com/products/details/video-aerial-systems-minion-pro-antenna-rhcp-sma-short. Not only do they have higher gain than the majority of antennas, they have a very good axial ratio.
The other thing not mentioned in the video is what are you using on the receiver side of the video link? What RX are you using? Does it have diversity? Lots of questions as to what the whole setup is. More power does not always equate to a better signal either. I have run a mile out (GPS distance on OSD) on 200mw with 100% video rssi.
Cheers!
LitterBug