Sold As Sixe Bottles Per Box

[formar]

Suppose there is some ketchup for sale. The ketchup is bottled and the bottles are packed into boxes. Each box holds six bottles. A store sells the ketchup in such a way that a consumer must buy a full box of six bottles of ketchup instead of the individual bottles. To describe this situation, I thought of a few sentences:

"The ketchup is sold as six-bottle boxes."
"The ketchup is sold as boxes of six bottles."
"The ketchup is sold as six bottles per box."

It seems all three are usable English, as all three patterns are found on google. But are all three good English?

[Tdol]

I'd use six-pack

[SoothingDave]

Ketchup sold by the case only.

[konungursvia]

I would use "in" rather than "as" in your sentences, which seem acceptable to me otherwise.