I think that gasoline diluted with ethanol is one of the most pervasive examples of how the wealth has been stolen from us.
There are multiple ways to view it, but the simplest way to think of it is that folks spend more currency for less gasoline at the pump.
The price of gasoline changing doesn't matter if it keeps getting diluted. The real price of gasoline is the 100% pure stuff. Bucc-ee's tends to have it for less than $4/gal, but most stations sell it for $4/gal and up. Plus, it's an effort to find it. Most gas stations sell only adulterated gasoline.
Just my two cents.
* the primary reason for the addition of Cat converters was originally 'unburned hydrocarbons', basically burning unburned fuel in your exhaust that made the exhaust stink. Modern cars actually adjust the fuel mix to be rich-then-lean-then-rich to keep the cat converters from loading up. The Cat converter adds backpressure which reduces engine output for the same fuel by 5-10% (which is why the first thing ricers do is delete it).
* cars used to run lean, which produces, in most cases, the same engine output for a huge savings in fuel. This is the real cost of emissions requirements, as lean-burning causes NOx production, which the EPA classes as a pollutant. Thus, cars were required to run rich (as the extra fuel actually cooled the engine cylinder through evaporation below the point that NOx is produced), which then made the unburned fuel itself a pollutant, and thus the Catalytic converter was also required.
There is more here, but basically older cars (2000-2015) that are fuel injected but used a hackable ECU (e.g. the Trionic systems, older ford ECUs etc) can be modified to literally produce more power while using less fuel.
And then there is the constant suppression of new engine technologies. For example:
* water injection, which allows EXTREME leaning of the engine without knocking while also preventing NOx
* Plasma ignition, which some automakers briefly experimented with. Basically, ignition science is weird, and using large corona wires to ignite engines actually produces a faster burn with less knocking as compared to spark ignition. Faster burn means max pressure is reached faster, which means more work done on the crank and not wasted in the exhaust.
* and then you can actually combine the above to remove the butterfly valve on the engine, which only exists to allow the engine to run rich while at low power levels (where normally it should just be running lean). Pulling a vacuum against the back of the butterfly valve requires work, and is usually considered to waste between 6-15% of the potential output of the engine. This is the primary contributor to so-called 'pumping losses'.
As a fun fact, adding a butterfly valve to diesel engines is the primary reason modern diesels get fuel economy only slightly better than gas cars, vs the lean-burn diesels of old that could get 40-60 mpg while hauling people, cargo, and a lead-footed driver.
Seriously, the reason most ricers start with exhausts is because it is easy as heck and adds essentially free power that never should have been removed from our engines in the first place.
There is a new caveat - modern ECUs will detect this and try to penalize you. Generally, if the ECU can't vary the fuel richness and see a corresponding variation in the O2 sensor (called 'closed loop operation'), it throws a check engine light. In older cars, the error was the only thing you got, and you could get around it by changing the engine tune to stay in 'open loop operation', which is the default mode when the car coolant isn't up to temp, and in yesteryear also when the check-engine light was lit.
Ever since 2008 or so, cars started punishing you by running extremely rich if this detected, called 'limp home' mode. It is a completely unnecessary mode that can foul up your O2 sensors and exhaust valves, cause backfires, etc, but fortunately you can tune the car's fuel maps (which most tunes are set to disable the penalty mode altogether).
So, basically yes, through an exhaust install and a quick tune (which you can either do yourself or buy offline), but anything beyond that requires some pretty heavy mods.
Catalytic deletions, and ECU flashing / reprograming can end up costing you a ton of money, if you get caught.