Depends on how many clowns you want to raise. I raised my first two Amphiprion melanopus in 1981 inside a small plastic tank that I hanged into the parent's tank.
I cultivated the rotifers and algae in 2 liter soda bottles. The most costly was the rotifer culture starter, everything else was cheap.
When I did it about a decade later on a more commercial scale I used specially designed tanks. With those I got up to 95% yield out of a hatch. The best thing was that I didn't need rotifers since my clown larva were able to take freshly hatched brine shrimp from day one. And due to the tank design I was able to switch them to frozen food around day 5. But this setup cost quite a bit.
The really costly part is the grow out. For that you need large tanks, feed a lot and do frequent water changes.