The same is true of batteries. You don't get more energy than you put into it. Fuel cells are just another form of batteries, but with a far higher energy density and much lower material costs. At best, you can claim there is one more step in fuel cells than with batteries, but even this is not necessary. Metal hydride hydrogen storage currently exists and can eliminant the compression step.
The notion that batteries are superior than fuel cells at utilizing low cost electricity is fundamentally in error. People have traditionally made the argument batteries are more efficient, but the gap is continuously shrinking and likely will become a non-factor. Meanwhile, you benefit from lower weight, less material cost, faster refueling, cold weather performance, and various other advantages. So it could easily be more cost effective to power a car using hydrogen than with cheap electricity than with batteries in the majority of cases.
> Sure, if you use grey hydrogen created from natural gas rather than green hydrogen created from water and electricity. Grey hydrogen is far from carbon-free.
You're conflating two different things: fuel cells and green hydrogen production. Fuel cell cars are in a lot of ways already competitive with battery electric on their own merits. Hydrogen production is going to be dependent on electrolysis. Even so, as electrolysis costs come down this too will be become cheaper than fossil fuel sources of hydrogen
It's also a lazy argument, as fuel cells have the possibility of being zero emissions the same way batteries have. In fact, this was repeated against battery electric cars historically, since electricity production is heavily based on fossil fuels. So repeating it against fuel cell cars is just playing the role of luddite again.
> That's a strong claim, given that battery prices have historically dropped 80% per decade and show no signs of slowing down.
That's from a very high base and is misleading. Regardless, fuel cell costs are also dropping extremely fast, but unlike batteries don't have the floor of material costs. It's likely that fuel cells will be much cheaper than batteries in the long run. Toyota for instance believes that a fuel cell car can cost the same as a Corolla. Electrolysis costs are also dropping in a similar way and you can expect green hydrogen production to be minimally capital intensive.
> The lack of hydrogen filling stations is the biggest roadblock for this among many big roadblocks.
It's starting to look like the hydrogen refueling infrastructure will be cheaper than the equivalent battery charging infrastructure. Some recent studies are suggesting this.