I find it ironic that I live on an island nation and yet fresh fish are a luxury item because they are priced so highly at the big chain supermarkets (often $18-35/kg for fillets). Supermarkets also tend to stick a few popular fish like salmon, trevally, and tarakihi. Fish can be far more affordable by finding a local fish market or fishmonger and buying the fish whole.
Most places will offer at least basic services for free (like gutting, scaling, and top’n’tailing) and some will also fillet for free (although others have a small charge). With a whole fish you can get far more flesh when it is cooked and for a much better price. The central fish in the picture (with the dark speckling) are mackerel that were on sale for $5.99/kg. The whole fish was $9 and once the head, tail, fins, spine etc. were all removed and it had been prepared at home there was still 850g. That makes it an excellent price by comparison with fillets at a fish counter at the local supermarket.
It can also be fun at a fishmonger to look at the huge variety of fish and choose one that you haven’t cooked before. You’ll find that the fishmonger can give you some advice depending on what cooking method you’re aiming for. In general you’re wanting flatter, thinner fish if you’re wanting to braise or fry, whereas you want a thicker fish to bake or fillet.
In the case of the mackerel, I had the fishmonger remove the head, tail, and guts.
At home I just needed a sharp knife and time to remove the fins, spine, large radial bones, and pick out a number of the smaller bones.
I kept a small portion intact to bake, kept a number of long pieces to fry (these potentially had some small bones in them to help keep the shape), and a pile of small fleshy chunks (completely deboned) to make into a pie.
I put each of my three piles (intended for three different types of meal preparation) into freezer bags and annotated them with what was inside and how it needed to be cooked. That way I could pull them out when they were needed instead of stressing about making a special trip out to buy fish and then needing to cook it all in one go.