Both can be built for a reasonable price. It really depends on the topography.
The problem, to make a long story short, is the curve radius. If you want to drive a train at a very high speed, you cannot have a very close curve radius. If you're in a more hilly or mountainous area, you have to build a lot of tunnels and wide bridges. This really drives the prices for building high-speed rail. If you're on flat terrain, then it's much easier, because there are no mountains. You can build the curves as you want to.
You have a lot of urban area. You need all of this urban enabling, to have space in the cities and so on. It's more suburban, as far as I know, so I don't think it's a big issue.
The cost driver for high-speed rail—to make it very short—is how many tunnels and bridges you need. In Europe, we have started with the easy stretches. The French started in the 1970s to build very cheap, high-speed rail lines between Paris and Lyon. The Spanish have done the same. The Germans started differently.
What remains in Europe today and the reason it's so impressively expensive today.... Right now, we're building high-speed rail lines that are more like undergrounds. For example, in Germany we have a new high-speed line between Stuttgart and Munich. This is almost completely in tunnels.
There is another factor that you may also know in Canada. This is crazy stuff from the U.K., where you have a lot of this urban enabling. That's something you have to do a deep dive into. There are reasons and lots of lessons learned from the U.K.
As far as I know, it's more about the complexity of the project organization. It's not driven by high-speed rail. That's very important.