Looking at prices of popular american retailers, the goggles go for around $275 (although currently sold out), the VTX and camera combo costs ~ $140 to $250, the standalone camera is $70 - $100 and the standalone VTX is $140 - $180. So yes, you're looking at more than 100 bucks on the video system for every quad you build. And if you crash it and your FPV camera breaks, or your VTX burns out, that would probably be another 100 to replace them.
Comparing that to HDZero, and you're off a few tens of dollars cheaper than walksnail. However, HDZero might not be the best fit for you and their goggles are more expensive. And of course you're off cheapest with analog 😉