What devices? Two routers or two clients connected to single router radio?
If your question is about two clients, then expected speed is around link speed /4. Lets assume you have common 2-stream AX clients close to the router, holding link speeds of 1200Mbps, 80MHz wide channel, no DFS channels used. In close to ideal conditions you should be able to transfer files between the two with about 300Mbps, or 35-40MB/sec. It can be higher or lower, depending on channel available bandwidth (other devices using it).