If you have to staff up a project from scratch, there’s a good chance you will not have all the skills and resources you need on day one. If you cannot beg, borrow or steal the resources from within your organisation, a common way to plug some gaps in your team, or bring in specialist knowledge, is to use contract resource.
Some of these guys are expensive, some are extremely expensive. But you have to weigh this up against what you get for your money. As they say, if you pay peanuts, you can expect to attract monkeys.
However, you cannot assume that because someone is expensive, they are any good; you have to apply the usual sensible measures when you recruit and select the right candidate(s). Check them out, interview them well, make sure they know their stuff and that you think thay will add value to your team.
If the ones you think are the best turn out to be more expensive than you’d planned for, then it’s down to you to make the decision on how you balance up your likelihood of delivering with an ‘A’ team or the cost of failing to deliver with a lesser skillset/capability. That’s what YOU get paid for.