Technology

Well, the data we do have is that the flight was just under 30 minutes and very likely under 100 miles.

From the Wikipedia on airline fuel efficiency:

The worst-performing flights are short trips of from 500 to 1500 kilometers because the fuel used for takeoff is relatively large compared to the amount expended in the cruise segment, and because less fuel-efficient regional jets are typically used on shorter flights.

In the example values table, the most efficient plane for a 560km trip burns 0.92 kg of fuel per km, so doing some rough math and assuming the electric plane travelled 100 miles, that would be roughly 148kg of fuel, or 50 gallons (190L).

At current jet fuel prices ( $3.76/gallon ) that's about $188 US in jet fuel as a rough estimate. It's unclear if the test flight went up to full altitude or if the plane was at full weight, so a fair comparison might have used even half as much jet fuel.

Edit: From some of the other comments, it seems like they might have only considered flight time as cruising time, not takeoff and landing, so my numbers will be quite far off if that's the case. My gut feeling is that this is probably the case, because this seems like too big a difference otherwise.

$5 for 30 minutes in the air. pick any speed you want. it doesn't matter. avgas and jet fuel don't compete with $5.

Batteries don’t get lighter as they’re discharged, so…?

JETTISON ZE PACKS!! PREPARE FOR LANDING!!!

The same way we make bigger aircraft with higher landing weights: beefier landing gear and structural reinforcement. Airliners don't have a lower max landing weight than takeoff because they have to, they do it because it's cheaper and more efficient. Add some more structural weight and you lose some payload, but if the efficiency gains from fuel cost savings make it worthwhile, then manufacturers will make them.

You can rethink the engineering with electric motors.

The planes you are describing are designed assuming they will be lighter on landing because of fuel. So why design them for take off weight?

Electric motors are condusive of blown wing design for example, and would have a unique landing profile. (The plane can land at much slower velocity)

Edit: yeah they've moved the engine shroud which allows for lower speeds. Given the same runway you would be able to trim vertical speed.

Fun fact, batteries DO become lighter when they discharge. But obviously not like fuel. But it's still a fun fact.

Literally the first sentence:

The first flight of the largest battery-electric aircraft to take to the skies lasted nearly half an hour while costing just $5 of electricity.

Can your Porsche 914 fly for half an hour on $5 of fuel ?