[lightbringer]

Originally Posted by RDF2050

I think it's because of the currency from SAO being somehow compatible with ALO. Since Asuna and him are "married" (share everything), his fortune must be huge.

Spoiler for contains spoilers for end of previous arc (no future content):

IIRC it really is his SAO money. The items got garbled but the money got converted. Kirito and Asuna are actually flat broke at the end of SAO because they spent almost everything they had on the rural house two weeks before the final battle, and they even had to sell off some of their items in order to afford it, but let's just roll with it.