For Mesh, you will need several units.
For normal WLAN, you need the router and several range extenders.
I see no difference on that point of view.
Mesh WLAN system is expensive only because they are new.
WLAN is WLAN, they said 600mbps...that is only several meter from the router and using eye sight distance, no walls, etc.
It does not matter if it is mesh or with extender.
The different between using repeater/range extender and mesh:
https://www.lifewire.com/mesh-network-vs-range-extender-4148022