So is that the way you trade? As for me, if I traded 8,000 lots 5 years ago (using your analogy), I'm pretty certain that's what I'm trading these days as well. So in the end, my costs would have gone up quite significantly.
A simpler way of looking at it.
Lets say you day trade 1000 shares at a time of TESLA and it trades at $50 a share. And you tend to average a 1 point stop and 2 point target.
TESLA doubles in one month to $100.
At this point, if you are trading off the same signals, you should probably be averaging a 2 point stop and 4 point target, and cutting your lot size to 500 shares instead of 1000. And so paying just half of the fees.
A year later tesla is trading at $500.
At this point you should definitely be using a much wider stop than 1 point, probably be using a 10 point stop and 20 point target if trading the same type of signals, your 1 point stop definitely wont work anymore for your signals, and you will get stopped out so often. And because you now use a 10 point stop you should also switch to 100 share sizes to keep the same risk, so you end up paying just 1/10th of the fees!!!
(Stock splits ruin the above scenario, if TSLA does a 10:1 split, you are back to trading 1000 lots again)
The same thing applies to stop stock indices except the double time is longer and so you don't notice it one year over the next.
But over 5/10/20 it becomes very noticeable which is what my original post illustrated. Im effectively paying 1/6th the fees for trading ES as i was paying 20 years ago and about one half of what i was paying 5 years ago.
Luckily ES has never done a stock split. CME created smaller new contracts instead ie. the Micros. A split could happen one day if the notional value keeps on rising like it has.