Originally Posted by mstateglfr

Bottom bracket- Um...just buy one. They are like $15-35 depending on retailer, time of year, and sale. Pretty sure 105 and Ultegra BBs are the same.

Chain- shimano or kmc- there are multiple options at the Ultegra level and vary in cost. Just buy whatever is cheapest at that level. Hg601 and hg701 are basically the same weight. And I am not convinced the extra pink process for a 701 chain actually matters.

Wheelset- btlos or lightbicycle. Look into both. Pick your hub, pick your rim, pick your spokes.
You mention you like 9000 and 9100 wheels and typically get 40k mi out of them. First off, which wheels are you even talking about? There are probably 10 different wheels under the 9000 and 9100 lines. Secondly, those lines have been around for what...11 years? And you have gone thru enough wheels to have a 'typical' distance they last? And that distance is 40k mi? If you have even gone thru 2 wheelsets in that time, that's an instance amount of riding year after year. Thats 8,000 yearly for over a decade. Impressive. I wouldn't use 'typically' for anything fewer than 3 or possibly 4 examples of something, but even at 2 wheelsets that's impressive.

Pedals- who cares. Buy want you want. There is a 40g difference between 105 and DA. Oh, and an extra bearing for longevity/stability in the DA pedal. If that matters to you, then buy it.

Cassette- Ultegra or 105, whichever is cheapest at the time you are looking. DA is bonkers expensive for the differences.