Here's another one cooked by my partner. It's really very simple, and tasted great.
Cost: Moderate ($16.50 bought a fish sized to feed two, with some left over to throw into a risotto the next day).
Peel and slice the potatoes, then toss in olive oil:
Bake. Baking paper saves dishes.
Sliced olives and fresh thyme. Put some into the cavity of the (cleaned and scaled) fish:
Put the fish on the potatoes, then scatter more thyme and olives over the dish:
The finished product is shown at the top, but here it is on a plate: