Should you develop them for a small $10,000 project? No. Should you use them if they have already been developed and are appropriate to what you are doing? Absolutely.
That being said, if you can spend any time at all creating some high-level personas (based on real people and data) it will add value – just don't spend a lot of your (limited) time doing so.
Some benefits of personas: It gives the team a common baseline that that they can use to discuss what features should be included and how such functionality should be framed and prioritized.
Finally, personas are not "a waste of time," as some may say, but are useful tools to support design efforts. It also gives the team something that really helps: empathy. You are creating something FOR a person, not just executing use cases.