However, my bigger concern is that working out the requirements is being done by someone other than the developer that's going to be working on the project. If you're trying to get something done on a budget, fewer people in the mix is better.
Furthermore, the conversation about product requirements needs to be a two way discussion. Developers are often in a unique position to guide a product owner into what's easy to implement and provides the biggest "bang for your buck." Their early insight can radically shape the product and is not based on what the customer thinks they need, but what the customer communicates their goals are. This is where a consultant can provide serious ROI to a product owner.