Process of producing c-Si panels has become a lot cheaper but this doesn't apply to GaAs process.
https://www.nasa.gov/mission_pages/station/structure/element...
Space applications are now mostly using triple-junction cells with GaAs as one of the layers. Spectrolab, Azur Space, and SolAero's product lines are dominated by triple-junction cells. Azur Space also still sells space-qualified silicon cells (lower efficiency and much lower radiation tolerance, but cheaper):
http://www.azurspace.com/images/pdfs/0002162-00-03_DB_SIA.pd...
The Martian radiation environment is mild enough that crystalline silicon might still be competitive if you needed large stationary arrays. But on the Martian surface, where you can't rely on near-constant sunlight, nuclear is going to be tough to beat. (Orbiters are a much better match with solar.)
That was 20 years ago, on a government contract, for panels that must survive the rigors of actual space.
Panel manufacturing costs have dropped almost 10x since then, and the environment (assumed under the protection of martian atmosphere) which they will operate will be far less extreme than Earth orbit, necessitating less expensive materials. I'm not so sure your numbers account for this.