Yeah, there's no contention AT ALL up to the DSLAM. DSLAM is DSL Access Module. Every DSL customer has their own dedicated copper pair from the DSLAM to their house--- it's their phone line. There may be congestion between the Central Office where the DSLAM lives and the rest of the internet, but in practice that rarely happens. The big limit on DSL is getting reasonable speeds a mile down the line over ancient copper pairs that were never intended for the purpose. Don't people remember the old Cable vs. DSL commercials, where the DSL companies were showing cable customers furiously calling each other bandwidth hogs and telling them "log off!"

DSL seems to somewhat taper off at 100 MBit/s over here in Germany, but that's actually quite reasonable speed for non-business customers, with 1080p taking 27 MBit/s.

I once had cable in a crowded neighbourhood, it was pretty terrible at peak times.

Isn't the speed of DSL highly dependent on the details of the actual analog line?

I have an ADSL line, and my contract says "50Mbps", but I rarely actually get over about 4Mbps. As far as I can figure, the reason is because my house is near the limit of distance from the central office... (the phone company actually has a calculator web app thing that lets you plug in your address and get the line length...and then a separate calculator that maps from line-length to expected speed)

[I'm not complaining or anything.... It's a cheap line which I've had for ages, they're very up-front about the caveats of ADSL, and I could easily get fiber or cable (from multiple providers) for a bit more money. So far I just haven't cared enough to change it.]