so as far as i can tell now, step up transformers take more wire to make than a 1:1 isolation transformer.
What gives you that idea?
Two transformers, of the same power rating and frequency, typically have similar quantities of copper and iron.
A step-up transformer boosts the voltage and reduces the current.
A step-down transformer boosts the current and reduces the voltage.
An isolation transformer theoretically has the same current in the primary and secondary windings. In reality, there's some loss, so it's not perfect, but don't worry about it at this stage.
The higher the current, the thicker the wire needs to be. A step-up transformer will have thinner wire on the secondary winding than the primary. An isolation transformer will have the same thickness wire on both the primary and secondary.