Vodka is ethanol and water, which is distilled. The end product is essentially captured as it evaporates and re-condensed into liquid. The original starch may or may not be completely consumed, but it will not exist in the end product.
If you want inexpensive starch, go buy some Niagara or Magic Sizing, about $2-3 at the grocery store. They work great and are probably less expensive than Vodka (which serves no purpose other than maybe to keep the lavender oil in suspension). Also, the alcohol itself will evaporate over time, leaving water and lavender oil.