Alex,
Nonsense!
The build quality of the 50mm f/1.2L justifies the purchase. It's not quite a hand grenade (a la 85mm f/1.2L) but, it's very close.
Like you, I traded up from the 50mm f/1.4, which is a great little performer for terrestrial use. All my early astro work was done using the 50mm f/1.4 and the 50mm f/2.5 macro. Once stopped down to f/2.5 to f/4, the CA was greatly reduced.
The 50mm f/1.2L is a beautiful lens. Well, I love mine, anyway.
Regards,
Humayun