It works, sure. But you'd have to deposit good amounts of bitcoin for your mining plans to actually make a bit of money.
Investing more money in cloud mining doesn't mean that you'll be making more money percentage wise. In other words, whether you invest $100 or $1000, it won't make any difference.
They are mining (I don't believe they really are, but just for example purposes) anyway, which doesn't change even if people don't actually invest one single penny to buy their cloud mining contracts.
This basically means that every person, regardless of his investment amount, ends up making the same profits in percentages. It's actually a great thing, but the rotten nature of this industry makes everything look bad instantly.