To be profitable the prices would need to go up for more than 30% on average, because 30% only get's them to break even if you assume zero changes in ridership.
There are a few costs like background checks that may go down when they stop expanding, but fewer than you might think.
And I used uber or lyft to ride back and forth to work every single day because it's so cheap. ~9 bucks compared to a 3 dollar metro ride (and I typically save 20 minutes). If it's 15 dollars I'd ride less often and I'd probably try to hail a cab first.
Oh it's definitely elastic. I used to take Uber everywhere, until they (apparently) removed the restriction on driver's to use nice/current cars. Once drivers starting showing up in 10 year old beat down cars, my riding plummeted.
Even if they cost more I have no idea how I'm going to get around when I travel. The other options are so disgusting I'm not going back to that.
I would use them even if prices went up 30%.