Your premise that Cost of GA has remained constant is flawed. Attached are two charts that show it has grown far faster than inflation and the cost of automobiles.
There are 4 factors that has killed GA:
1. Cost. This is made more challenging because the economies of scale are not working in this industry. When you only sell less than 600 GA (non-jet) aircraft a year and only have 30,000 active aircraft in the US active; you are going to have a very expensive ecosystem.
2. Tort and Liability: The summary awards agains GA industry has caused the premiums for GA businesses to approach 50% of the costs. Each component has to factor their tort cost in to their products and services. They have to apply their fixed cost to each unit sold. This makes for very expensive units.
3. Government regulation. It is intersting to compare the Boating industry to the GA industry. One is regulated at the federal level by the USCG; the other by the FAA. The FAA applies the same methology and oversight to GA that they do to Commerical aircraft and airlines. Notice the USCG does not. If the boating industry; which kills 6x more people every year than GA were regulated like GA; it would die also.
4. The press has sensationalized all the tragedies of GA and has scared the public. This has impacted insurance companies as well. There are very few major companies that will allow their employees to use their personal aircraft like they do person automobiles. If that one factor were change; it could go a long way in reviving GA as many individuals would use a GA aircraft to do their jobs rather than airlines. And that is why it will never happen, because the airlines have had a systematic approach to killing the charter and personal aircraft business for 50 years.
I think GA has a strong case of instituational descrimation and will require protection to survive now. The economies of scale are now killing it. Cost of fuel is going up, cost of products and services keep going up. Only Corporations will be able to use GA as it still can be a business deduction. Most individuals will not be able to use it in the future.