No that's not really the case either because the unit there is the singular diamond itself, carats only came up in reference to diamond
dust not being measured in a standard in a standard unit
☆ because the source makes it dirt cheap & people were asking economic questions & complaining d&d is not an economics simulator while taking the
obvious economics answers answers to make bonkers 1:1 conversions that only served to demonstrate how the current setup invites trouble.
That single gem worth X simplicity breaks down when the component is some kind of commodity like
[gem] dust worth x ,
literal trash worth x (should be trash &
[expensive thing worth x] or the labor involved in engraving that trash should be part of the casting time. Multiple diamonds worth x so on furthers that problematic trend since the higher tier spells can be ungated & unthrottled by buying costly components for lower tiered spells.
There are further problems involving overuse of a singular component defeating the entire purpose of gating spells behind a costly but not consumed component used by a laundry list of spells though.
Your 295 gp diamond does not work for a spell that requires
a 300gp diamond
☆ ie one pound, three standard vials, etc