Well, $265 (+antenna $60), but I purchased an Emlid Reach M+ [1] for drone RTK experiments, and it has been pretty simple to use... comes with a really nice UI on the device and internal storage in the unit. Also their website has good documentation, which is helpful since there is a lot to learn about how to do RTK.

Found a local NTRIP caster (within 10 km, lucky I am in range of a public RTK2go one) and the Reach uses the mobile hotspot on my phone to connect to the caster. After a couple seconds to minutes, it settles down to a 10-12 mm accurate fix in lat, lon, alt, and is kinematic so it maintains the accuracy as I am flying the drone around. It records the whole thing internally, or you can have various output modes like standard NMEA over serial, or bluetooth to your phone.

Also, I have used it to record data internally then post-process it for PPK using the county's publically-available RINEX files [2] and Emlid's RTKLIB fork [3].

[1] https://emlid.com/reach/ [2] https://geodesy.noaa.gov/CORS/standard1.shtml [3] https://docs.emlid.com/reach/common/tutorials/gps-post-proce...