It's like cars. Getting 400 horse power out of a 350 is pretty easy and inexpensive but getting600+ horse power out of that same engine gets very expensive and time consuming.

That's the same with bows. Getting a bow that is quiet, gets good speed of about 300 - 305 IBO, has a decent brace height of 7 inches,etc... is relatively easy to do today. But getting one that shoots 320 - 340 IBO, is evenslightly quieter, with a slightly longer brace height, and vibrration freegets very expensive to engineer and manufacture.