I use shapeshift for several times, they're legit. But, sometime you will get some delay (about 1-3 hours in my case), not a big deal for me. I don't think they're expensive, since they're legit and reputable.
On my coinomi wallet, there's another instant exchanger called
Changelly, i personally never use it before. But, since its on coinomi, i think they're legit.
Never heard about cryptoket.