the good thing about downsizing parts like that is that inherent strength usually goes up
but yes, it may still cost a packet and work out a little more expensive per foot than an f18 but if it keeps sailing for over 30 years like many of the nacra5.2s it will have been worth it
in 1977 the nacra5.2 cost $2,950
35 years later the same boat costs about $1000
that's $70 a year
imho a slightly heavier boat from an established builder is the best buy for most sailors