Yeah, making your own bones will be the far cheaper way to go - even the cheapest pre-made bones are going to cost you an arm and a leg. **rimshot**
You can make some pretty nice femurs, tibiae, fibulae, humeri, radii, & ulnae quickly and easily from foam board - cut out the rough shape, grab a sanding pad, and start shaping the bone. Once it's "close enough", paint it with some latex paint to seal it, and then add aging (paint, stain, etc.)
I've made hands that work out well, also from foam. You can shape an entire hand as a piece, or do the carpels as a group, then the metacarpals and phalanges separately, and then run a wire through them, to make a pose-able hand.
Ribs are simple with foam - thinner sheets of foam work great for it (cut curved bits - there's the rib. Shape lightly with sandpaper and then paint 'em up).
Scapulae are fun - takes a little more skill, but so worth it.
Vertebrae are best done in batches, as their intricate shape make them fragile, and they become tiresome. Batches are easier, and more rewarding as a final product (in my opinion).
Skulls take more work, but you can find all sort of tutorials here on the forum and elsewhere on creating your own skulls en masse.
edited for a spelling error of the sort I can't let slide
I made a bunch out of plaster for a bone wall. Just cut plastic ones in half you have 2 molds. They would work in a sheltered area I don't know how well they would hold up in the weather, mine are a bone wall under the porch so they are not in the rain.