How do you ensure quality? I usually find 4-5 people for the same tasks and 1 or 2 are in the end to my expectations.

I review their portfolio and create a sample task to see how communication goes along and then if I am satisfied I place real order. It is not expensive so I can try few people before commiting to some more work. I find this website extremely helpful. I also like that this website enables artists from impoverished countries make living.

Aren't the prices usually low enough that you can have the work done multiple times and choose the best one?

That's my approach. Want a logo for a project? Get it done by five different people instead of having one person do a few iterations. Over time of course you find people you'll go back to for specific types of work.

Yep, it's pretty much the way you do discovery of quality work in this sort of market.

I've commissioned vector artwork from 3-4 people and just picked the best one, and then kept working with that person going forward.

That's usually how it normally works with creative agencies in the industry. You brief them and they come up with a creative work, but there's always several rounds of back-and-forth to get refine it to the point you want it at.

Do you pay all the prices, then I don't know that it would be cheap. Do you not pay the ones you don't choose, then I'm not sure it's ethical.

At some point, I needed a logo for my hobby website. Nothing fancy, just better than what I could cook up with my non-existent creative skills.

I asked 5 different people on Fiver to create one for $5 each and chose the best one.

This is obviously an example on the low end, but you could expand this to the $500 dollar range per designer for a full website template and still end up with a decent looking thing for $2500.

I do but having to weed out the obvious template modifiers first is very annoying. In particular for design tasks (logos, infographics, etc) you have to look through at least 20 profiles before getting an idea on who is having original ideas and who is just modifying the same 50 templates over and over again.