I've always stuck with entry-level MacBooks for that reason - it's a more reasonable amount of money to lose and allows me to not care too much about it even in sketchy situations where you wouldn't want to bring a 4k$ non-waterproof device.
M1 Ultra has 90% better performance than the "fastest 16-core PC desktop chip available", which is probably the 5950X.
M1 Ultra has better performance than the "highest end discrete GPU available" (probably the Radeon RX 6900 XT?) while using 1/3 the power.
So I'm not exactly sure I'd call your build same ballpark, and I also can't imagine it was only slightly over $2k given that the CPU[1] and GPU[2] you specified alone cost $2200 on a good day...
The 3080 beats the Ultra in perf for games/ml. The 5950x is not 90% slower, but it is slower.
Like I said, it's not going to be equal to the $4000 M1 Ultra. But it's in the ballpark (and does beat it in certain use cases such as games/ml).
The thing is these are 2 year old parts at this point. If we see 4x series from nvidia and/or Zen 4 this year all this could change dramatically.