How does that work? Because you're right it is a bit pricey.
Collect willow twigs, trimming the leaves, immersing the stems in a pail of water, and pouring the water on newly planted trees, shrubs, and bedding plants. Commercial rooting preparations contain a synthetic form of indolebutyric acid (IBA) and growing tips of willows contain high concentrations of IBA, depending on the quantity used and length of time you soak them. Any willow (Salix) tree or shrub species will work.
A great way to make your own rooting or plant tonic for cuttings, transplants, houseplants, vegetable plants, herbs, whatever you want to grow healthy strong roots. The salicylic acid encourages rooting and triggers natural defenses against bacteria, fungi and viruses.