Its so interesting that the difference between Indy and F1 in terms of lap times is objectively marginal but subjectively extreme.

I would have guessed given the extreme cost difference between them there would have been a significant gap (like 30 seconds) but the fact that it’s only a few seconds difference is surprising.

I'm not sure it is objectively marginal. At Circuit of the Americas where they have both raced recently the difference in lap time is about 10 seconds. That doesn't sound like a lot but is close to 10% of the lap. The F1 race is 56 laps so by the end an Indycar is going to be 5 or 6 laps down. Throw in the fact an Indycar can't do 56 laps without refueling and it might be closer to 7 laps. In motorsport that is extreme

Getting faster is hard and expensive really. You can be pretty cheap and still be quite fast.

On other side, F1 has for very long time kept speeds down when new innovative ways to gain it has been discovered. For some reason I can not understand drivers and spectators dying in accidents is bad look for the sport... As such it really is not best we could technically do.

making a car go fast on a straight bit of road is relatively cheap. making a car take a corner a couple tenths of a second faster is very expensive. and there's only so many corners in a lap. add up those tenths - that's your few seconds of difference!

Not really. F1 regularly changes the rules to make the cars slower for safety reasons.

F1 is on a completely different level than IndyCar. The drivers are also on a different level compared to anything else.