Cost goes down significantly for subsequent years personal. Currently at less than $200 yearly.

Unless you need System Modeler, in which case add another $576 perpetual + $260 annual.

There is a combined license for Mathematica + System Modeler, but it's "Contact us for pricing". Mind you, that's still on the Hobbyist tier. You cannot use its output for anything commercial.

Contrast with Julia's MTK/Dyad that are free for non-commercial use.