As the drop-in replacement for XQD and the logical successor to CFast 2.0, CFexpress is the hot new format that’s most definitely here to stay. But CFexpress cards are still relatively fresh and new… and expensive. While 256GB SD cards can be picked up for as little as $54, and even UHS-II ones can be found for under $100, 256GB CFexpress cards typically start at around $200.
But there is another option, as detailed by Joseph Nuzzo over on Photofocus. You can also use an M.2 NVMe SSD inside Sintech CFexpress Type-B M.2 NVMe 2230 SSD adapter. NVMe SSDs are significantly less expensive than CFexpress cards, allowing for larger capacities for less money while still being able to get the speed capabilities for which you need a CFexpress card in the first place.