But here's the thing: this train I'm talking about _is not_ an ICE, it's a _regional_ train, but it makes only one stop, and cruises at 160km/h. And being a regional train, I can ride on the Deutschlandticket, which costs 49 euros a month. Even if they raise the price on that ticket (likely), it will still be worth.
Good regional train services is the key to this problem. Provide nice services into the cities, allow those towns to densify around their station, and that will relieve the pressure.
I've noticed a similar thing here in Berlin with some of the surrounding commuter towns.
I certainly hope the Deutschlandticket stays at the current price; but you're right, it will still be good value even if the price goes up — even the more expensive BVG ABC ticket is still only around 1/5th the price of a UK Cambridge-London season ticket.
Unfortunately, the UK does not have particularly good train service any more, thanks to cuts made in the 1960s: https://en.wikipedia.org/wiki/Beeching_cuts
As context, for people not in Germany: each transportation region sets their own prices, but the new (nationally subsided) €49 ticket is already cheaper than monthlies in most places. This is good and convenient for people living in downtown, but it is a godsend for people living in suburbs, because their distance-based monthlies were sometimes two or three times that. For people living in the edge of a region and commuting to another, it was even worse, as they needed tickets from both regions.
I believe the equivalent "legacy" ticket on Deutsche Bahn (all regional transport free) was something like €212/month. €49 is one hell of a deal.
Unfortunately, it's mostly in places where people don't want to live, because there's no jobs in those areas.
The places with the jobs have severe housing shortages. Some of those shortages can be resolved by building more homes, but there are also places which look great right up until you realise they're on a flood plain.
But even the places where you can build more houses, if you just do that without also improving the surrounding infrastructure, you'll end up with horrible congestion… and if you're building infrastructure anyway, you should put that infrastructure in the places that already have houses so that businesses will want to start up there.
Unfortunately, the UK government keeps cancelling the bits of infrastructure that would help: https://en.wikipedia.org/wiki/High_Speed_2