The cheapest units that are still genuinely worth owning.
You don't need to spend three grand for a small, mostly-flat lot. The catch with budget units is coverage (most cap around a quarter acre) and slope (gentle only). Within those limits, these mow reliably and pay for themselves against a season or two of lawn-service invoices.
Lowest upfront cost of any wire-free unit. A magnetic boundary strip replaces buried wire and vision helps it cope with some shade — strong for tiny lots and fast payback.
The coverage-per-dollar value leader for a standard suburban lot. You do bury a perimeter wire, but it's the cheapest way to mow a half acre on autopilot.
The cheapest credible wire-free mower. RTK satellite positioning, no boundary wire to bury — best for small, open, fairly flat lots.
Step-up i-series Navimow with better mapping. Wire-free RTK for small-to-medium open yards; wants clear sky for the GPS fix.