Are you saying those who go to RFP to keep cost control transparent really don't need the help? It's also kind of egotistical to assume a company needs you and you alone to solve their problem. If the problem is big and important enough, rest assure there's more than one shop that has an idea as to how to fix it.
I also think we're talking apples to oranges. A one person shop may approach contracts differently than a shop with 13 across 3 time zones.
In 10 years of consulting, I've yet to see a client buy this line of thinking. Clients want an accurate forecast for cost and key assumptions being made to formulate that cost. At the end of the day, it's in their best interest to get a good price.
This doesn't mean you can't over-forecast the hours needed in a week to deliver x, it can be an iterative/incremental process. But don't think for a second a client won't want to see how you came up with your pricing model before signing an SOW.
There are two sides to this. Most clients will want some form of cost control on their end. If the final proposal has ambiguity, you best bet the client's procurement team or relationship manager will want to discuss this. They have people they report to as well, and it's in their best interest to get the best price. The forecast has to have some form of predictability/reliability, otherwise prospective clients will simply stop returning your emails.
I also think we're talking apples to oranges. A one person shop may approach contracts differently than a shop with 13 across 3 time zones.