That works if you can get your clients to agree to it, but most clients won't. Hell, cost-plus is almost always better for the contractor than firm-fixed work

That works if you can get your clients to agree to it, but most clients won't. Hell, cost-plus is almost always better for the contractor than firm-fixed work -- it shifts the risk to the client! -- but a lot of organizations just flatly refuse to go there for that reason. They want you on a firm fixed price schedule or not at all, at least for any sort of non-trivial work.