I wonderred about the same - my Lagoon 410 ist 9 to, the 450 (with only 4 foot more) has 15,5 to and the 500 has up to 25 to.
Because I am thinking about a bigger boat, I tested the 450 - it has a lot of weighting gimmckis which I donīt need and the interieur is made of 50mm massive wood
Additionally it has icemakers, 2 fridges, 2 freezers, a 15 kw power-station, etc.etc.
The difference between the 450 and 500 is again the much stronger material like a 100KG anchor
(450 has a 25 KG anchor) and additional space.