I paid a hundred or so for a dropper from CRC but it was pre-pandemic. Looks like it's still not too much more.
Cheap is fine, these are basically as high tech as an office chair. Cheap and used maybe not because the cheap ones have a sealed cartridge that can't be refilled or rebuilt.
The Rockhopper of today is a strange bike. Everything about it seems to encourage you to stand pat or buy a new bike, the possible upgrades are not in the direction of what everyone is riding
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Genesis 49:16-17