The brilliant and appropriate classic TI-86 calculator has been discontinued and there is no model that adequately replaces it. Many are too “advanced” to be used in schools, leading to schools suggesting Casio and other competitors which are inadequate further on. Other models are inadequate themselves.
The TI-86 could use an overhaul in power management (only alkalines having adequate voltage, AAA having poor capacity etc) and maybe a few other features but it is irreplaceable. People can only hoard from the second hand market now.