The difference is materials, quality and price.
Some of the 100,000+ yen Carbon bonnets on sale in Japan are a full carbon fibre bonnet panel, with an FRP skeleton frame underneath, meaning that when you open the bonnet, you can see carbon fibre weaving underneath. Legitimate 6-8kg bizness.
But most of them are an FRP "under panel/frame", with a carbon fibre "top panel". Cheap, look good, and do the job.