RFP; GIVING AWAY DESIGN TO GET THE PROJECT

I have been in the industry for more years than I want to admit. Over the last few years the special event/sports design business has become very competitive. We never had to go through the "request for proposal" process like we do now. I have spent weeks working on concepts, scope, presentation format, etc, etc. I work on a team so you add the time of a project manager, a sales person, a production artist, copy-righting not to mention sending a team of 3 people to the site or venue, it can get very costly.
More and more RFP's want a design component to it. Internally we are always challenged how much design to give away. Design and project management is our product so to give 2-3 design options and not to get the gig is not juts deflating but very costly to a small design firm. It is not uncommon to spent $10k - $20k to try to win a bid.
I am writing this because we are in the middle of 3 huge RFs at the moment. In fact, I am spending 100% of my time working on these projects. I have many stories of wins and huge losses.
I work for a Berkeley-based sports design firm (when I'm not freelancing) which has/had 5-10 employees. We were offered to bid on the signage/graphics on the new Wembley Stadium in London. They were knocking down the historic old Stadium and rebuilding it from the ground up. They wanted to bring the history from the old building into the new Stadium using the concourses to show images of great events from Live Aid and other concerts to soccer games to Royal events. I had a great time designing photo collages and researching the history of the London Stadium. Along with another designer we spent a good month concepting different options. We printed samples of our work as well. Three us flew to London and surveyed the new Wembley Stadium as it was being built. We had to take a 2-day safety course before we could roam the property and walk through the construction site. We returned after a week with survey data and drew up our scaled baselines and proceeded to formalize our designs. We are now 6 weeks into the RFP when we get a call that they have decided not to do the proposed design direction because the construction has gone over budget. We were not just devastated but financially in a hole. As a Company we had spent $20k and no way to recoup the cash. It almost ruined our little design studio.
This is just one example of many RFPs. In this day and age I still don't believe that design wins the bid. It's all about the mighty dollar and even though we put our little copyright line on each concept, it doesn't stop the potential customer taking our designs to the lowest bidder and revising a line here or a color there. It's tough to prove they "stole" a design. The RFP seems a great way to get free design and free services.
We are currently waiting to hear if we are a finalist on a bid for a National football game being played early next year. We had a team of 6 working out the initial presentation including hiring a 3-D modeling artist. If selected 4 of us are flying to another State to do a meet and greet. This is the nature of the business now. It's a huge risk and it feels very unfair. Many of these RFPs are for a one year contract so if you are awarded the project you have to make your money back on that one event and then spend the money again to go through the RFP process again to try and win it again.
Please share some of your own experiences. I know this is a hot topic in the design/event industry.