Engineering services ARE a commodity, subject to bidding on an hourly rates basis. We're all interchangeable widgets, don't you know?
There's a push for "qualifications-based selection" for engineering services on publicly tendered projects. That means the firm which can field the best experience list and resumes is supposed to get the work, irrespective of the price. They're of course free to put the "B" team on it after award, though. It can be and is used as a means for big firms to exclude low-cost competition springing up and eating their lunches.
Then there are two-packet evaluation processes, where price or rates and qualifications or technical proposal are sent separately. The old joke is that this just reduces the work of the bid reviewers by putting all the useless irrelevant information into a separate package that can go right into the shredder...But done properly, a truly "quality-based" rather than merely qualifications-based selection process at least has a hope of obtaining good value for money for services without resorting to a purely rates-based selection process or merely dividing the work up amongst the old boys club.
The best way to get paid properly for the true value of engineering services, in my opinion and experience, is to sell a solution or product rather than engineering man-hours. Incorporate work which embodies, and allows you to profit from, a portion of the savings that your efficient and smart design, selection and procurement etc., offers to your customer. Sell it on a fixed price basis with a defined workscope. Tougher to get screwed with non-payment that way than if you're providing only paper drawings and specifications.
Yes, you can get screwed doing this too. I've seen a detailed workscope I developed in previous employ, as part of a free bid for a fixed-price project, used by the "client" to direct the work of the lowest fee T&M bottom-feeder. Giving out free detailed proposals is a mug's game which in some industries is played by all participants.
My current business does "studies" on a reimbursable basis at reasonable rates, which define the workscope and give the client at the end of this work, a fixed price for the complete execution of the design. It takes us far less work, and far less of their money, to get to that point than competitors who follow the fee-for-service design, then multiple bid construction, model that is prevalent in our industry. It works well for our clients, who get a firm price for very little up-front investment of time and money, and for us in that we don't give our engineering work product out free of charge. We do respond to requests for free bids sometimes, but there are ways to draw the client into our more normal model even then, as seldom is their workscope for the project complete enough to allow an apples to apples comparison amongst bidders.