While they are certainly capable machines and probably have a decent blend of sport SUV attributes...... a quarter mil for a vehicle that is not top of it class in terms of brand (its a MB not a Bentley), speed, size, interior finish, towing capacity, or off-road capability seems a bit excessive. Not to mention their....a-hem..."styling", while not awful is also somewhat reminiscent of a filing cabinet on wheel.
You are also getting an ownership reputation mix of part Kardashian, part Rapper, part Russian Oligarch.
If I was to spend a quarter-million+ on a mid-sized sport SUV, I get a gently used Lamborghini Urus for roughly the same price give or take. At least it will be at the top of its brand and performance classes.
Outside of the Urus, there are a whole host of great mid-sized/two-row sport SUVs with a similar nice blend of features/capabilities and are honestly better looking vehicles for ~$100K less. BMW X5M, Audi R8 RS, Porsche Cayenne, etc.
If you want to stick with Benz, I would rather have an GLS 63 AMG at a significant discount to the G-Wagon AMG 63 and get the GLS's 3 row interior space, faster speed, better styling, probably better handling and ride, etc.
That's just me though. Personally I went "the poors" route and bought a Durango Hellcat for ~40% the price of the G AMG.
Good luck with whatever you choose to do, if the G AMG is the only vehicle that scratches the itch and you have a $250K burning a hole in your pocket than go for it.