not too sure about this; I just can't see how else to convey the meaning.
Literally, in English I don't believe there is a difference between cave (cellar) and caveau (small cellar)

without fuller context, but remember that "cave" is also the word used for the places where wine is made and stored prior to sale. Having purchased some wine, you might then store it in your own cellar, which is usually referred to as a "cave" as well, but maybe to make the distinction they are using "caveau" here.

Any wine-growing region in France will have its "cave coopérative", something much grander in scale than the wine cellar one might be lucky enough to have beneath one's house.

However, for me, the primary sense of "caveau" is "burial vault". I know with money you can't, but maybe you can take your wine with you ....