Let me reiterate what others have said about wood self-bows and add my own two cents because that is sort of my schtick...
Self-bows in the long run are by far the cheapest. Secondly, the first time you make a really decent shooter is nothing short of a revelation. You wont want to put it down.
Third, it adds a whole new facet to your life. It isn’t just about getting a bow and shooting it. It’s a new love and appreciation for wood, it’s properties and trees in general. It’s a connection to your gear and a sense of satisfaction that you will never understand going with factory made stuff. It’s a learning process of how things work and interact together, a process I really enjoy. Lastly, it’s an expression of yourself and your own creativity through primitive weapon making and hunting.
Can you tell I like this hobby yet?
I’ve never heard of a person go into this hobby who sticks with it long enough to be successful and come away feeling anything but a greater appreciation for nature and history as well as having a very positive way to spend their time.
So, easy answer: EBay.
Far better answer- consider making your own stuff. Just go in slowly and read a lot.