I know that not in the topic, but maybe someone will be interested. A few days ago I bought a SANDISK Extreme Pro SDXC 512 GB card on the Polish portal - SDSDXXY-512G-GN4IN for 60$ (279PLN). I tested it in a laptop reader and the transfers are the same as in SANDISK Extreme Pro SDXC 256 GB (purchased by me earlier in the official distribution). I also tested it in 5Dmk3 and with 240MHz settings in the record it has ~ 95 MB / s (analogous to the 256 GB version). The seller declares 14 days for a return and a two-year warranty (I assume that only in Poland, because we have such domestic regulations). I am not related to the seller in any way and I do not have any profit from this entry.
https://allegro.pl/oferta/karta-sdxc-sandisk-extreme-pro-512-gb-170mb-s-12543428724
https://allegro.pl/oferta/karta-sdxc-sandisk-extreme-pro-512-gb-170mb-s-12543428724