^ expensive parts are needed to work accurately at those RPMs, the parts also need to be lightweight etc and of course reliability.
taking in mind just one component like the pneumatic valves used would skyrocket the cost of any regular line of cars to reach those 20K+ RPMs that F1 engines were doing before.
pneumatic valves are not that expensive or complex... ducatis have been using them on street bikes for quite some time. the next wave will be electro actuated valving. no cams needed.
the main thing with high rpm usage are the wrist pins...they have more load on them than anything and control the load on the piston....you should see some of designs...crazy offsets on the pins to decrease friction. (i have a piston, ring, wrist pin. rod, iconel header, brake rotors, calipers, and sparkplugs and steering wheel from the petronas 3a engine used in a 1999 sauber c18)
to stay up front..teams will still throw crazy money at these 4 bangers cost never goes down only goes up....this was shown in motogp...nomatter what changes they made to cut cost...it kept creeping up till DORNA stepped in and told em to spend away. this is supposed to be better...its formula 1!!...its about progress nor regress.
if i wanted to see 4 bangers running around...i could just go watch the other formula races...