I think it was about two maybe three years ago I sold some cf hood vents just like those for about 80-90 bucks. That seemed to be the going rate for them back then. I think Paulo still makes them and sells them on a website.
If anyone is looking to get a hirev cf jdm replica vented hood I highly recommend talking to hi rev first and asking them if they can leave the vents off when they make your hood. Their hood vents are not as stout as the vents shown here. I believe the ones you have [pictured] are Paulo vents. Hi rev glues their vents onto their hoods, they don't bond studs on them. The problem with that is their vents aren't as thick, they probably used thinner cf weave or only one layer. After time the resin has began to crack a bit on my vents, even with the gold foil on the underside to try and reflect the heat.
In a perfect scenario, if you were looking to buy a cf jdm hirev vented hood, they would not glue the vents on, leave them off but wrap them and put them in the box. This way the new owner can bond some posts to them like the Paulo units have. Or hi rev would bond the studs to them, include some nuts and then put them in the box. Then when the vents wear out, one could just purchase new vents, rather than being stuck with vents that have resin that is cracking and deteriorating and no way to safely remove the worn vents without damaging the hood. They take massive amounts of heat being right above the manifold. My manifold is even wrapped with thermotec heat wrap.
Then when one receives their hood, they could drill/Dremel some holes in the skeleton underside and then attach the vents to their hood.
Just my opinion based on experience. My car us a garage queen too, it's not a daily driver, and I have the gold foil barrier. I'd be interested in seeing how some other people's hirev hoods are holding up to the heat and elements.