For bot price (selling), parts don't make any difference. Grade also doesn't make any difference other than meeting the requirement. Skills matter the most. I swap out good parts from bot that I want to sell on BBS (best price for the right customer). Sell the good parts to make extra money, or use them in my bots, or in bots for quests.
Not quite true.
If you're not at the cap on value, better parts will boost the price slightly (just not as much as the parts cost).
When I'm starting off and can't fully train my tech bots?
Or I'm starting combat sales and need a sale before I can train to A skill?
The sale value showing with my S-class "training" parts is about 8-10K more than with the C-class "sale" parts.
(of course, with 5-6 training parts all costing 10K each to buy; I'm not selling it with those to get 8K total)
And bot grade matters quite a bit, until you're price-capped. And you can hit the cap earlier and stop training.
A female C class combat bot caps out for the BBS sale at A skill and D Social. (sells at 200K at that skill regardless of parts)
A B class combat bot is already at cap at B combat skill (same 200K, less training to get to B class by a lot).
An A or S class bot I think is capped at C skill? (I rarely have them as I don't dump-dive much, and tend to save them for later)
But a C class at C skill sells for like 60-80K, and a C class at B skill sells at 140-160K.
(CMT-24 sells for the most, AGMX-9 sells for the least; there is actually a per-bot price adjustment causing most of that range)
So having a B class pickup from the dump to train saves you the B to A part of the training process.
Or the tech bot sales?
D class bot needs to be B/B Electrical/Mechanical to hit cap (75K), B/C or C/B won't get there.
C class bot can often hit cap at C/C (for the Techie bot, the lower sale value of the AGMX-9 can just miss the cap, 71K-75Kish)
Skills do matter a great deal (as high enough skills can hit every BBS price cap on any qualifying bot); that's true.
But class/parts can give you a bit extra to get there, or get a bit of extra value when you're starting.
Buying a Agp-Val or a Techiev2 at the flea market when you can only train to C/C?
The Agp-Val costs maybe 6K and sells trained for (if I recall) 45-50K.
The Techiev2 costs maybe 12K and sells trained for 75K.