Thanks for your reply! Good to know the breakdown of the costs as this could really eat into the profits.
I haven't done any detailed analysis on the slippage, execution side. At the moment, I'm just relying on the IB adaptive algos for trade placements.
Sometimes I also look at
(a) impact of partial fills
(b) impact of having no fill including unable to borrow
(c) impact on having a fill that didn't happen in a model
(d) impact of later data adjustments by data provider
The slippage I mentioned is somewhat easy to track since I have formal models of all systems.
Slippage could be by far the biggest % cost creeping into your trading. Likely double-digit %
My guess is - for most traders it is order of magnitude bigger than obvious costs like commissions.
So logically, everyone should be most concerned with their slippage. But looking at those things lacks excitement and probably looks like being a cheapskate. Who cares about executing at 58.76 or 58.77 anyway. Aren't we after big moves?

Val