I believe avionics uses mil/aerospace qual chips, therefore should not be a problem at -40.
That's why avionics is so expensive.
No it's not. Chip components are a tiny fraction of the built device price - perhaps 1%. The vast majority is profit and to a lesser extent insurance. This is followed by certification costs, QA costs, and materials.
Work on manufacturing costs of around 10% of final device price.
NB Software costs are often a component of the final price. But that is a fixed cost per product line rather than a marginal cost.