Dumping is really only applicable if they are undercutting their prices in specific regions. If I am under-charging across my entire lineup, that's just on me.
Which they absolutely do. AFAICT, Uber doesn't subsidize rides in Europe because predatory pricing is illegal there. But they do in new markets in the US and used to subsidize heavily in China, which opens them up to charges of dumping, it seems to me.
There's a bit of a difference on which government body enforces which rule.
In quite a few countries, taxi rules are governed by cities - so the municipality government is the enemy.
Anti-monopoly/ predatory pricing rules are at least national level - and if you are unlucky you can go against the EU itself, which historically has not been afraid to slap companies with gargantuan fines that would never be allowed from the pro-business USA SC.
Uber has lots of problems with legality in Europe. In Germany it's basically nonexistent. Note that the regulation for taxis in Germany really makes sense (for instance background checks for drivers).
I don't know what's the definition of "full" here, but I'd guess they leave the middle back seat empty. 3*18 is still 54 so there's clearly some profit to be made.
oh, that's a good point -- i was forgetting they can pair up 4 different paying customers. i think it must be rare though -- i see full ubers and full lyfts fairly often, but i've only ever seen 2 couples (& it's only $1 more for a pair).