Aside from Q's about opaqueness of different parachutes, etc.: I think price should be weighed against the quality. Some older chutes come in a pretty rotten state, some with the ties around the edges missing, and in general might bear little resemblance to what you think you're buying. Best way, unless you have reason to trust the return policy or the money doesn't matter, is to go look at what you buy before buying.
Even a partly torn, partial, or rotten chute (nylon, rayon, etc. can all break down) can work if used with netting underneath and netting or plenty of cord thrown over the top and secured to the stakes or framework.