The pirates don't spend their money on things like big boats and electronics. They spend their money on things like automatic weapons and rocket launchers. They pull up next to your nice, big cruise ship (or cargo ship) in a rickety old, outboard powered, skiff and threaten to send an anti-tank round through your hull if you don't allow them to board. Then, once on board, they hold the ship and everyone on it hostage.
They tend to be very poorly financed, and very poorly equipped. The one thing they DO spend money on is weapons.