It seems to me strange to try to model "appeal" as a function of independent variables which are the items selected by respondents. The independent variables would not truly be independent and level balanced. They would be based on the respondents' preferences, so the logic seems circular to me.
It seems to me you have two models: how prices and availability of items lead to choice into the shopping cart. Then, how the utility of each bundle placed in the shopping cart relates to the "appeal" rating scale. Tom Eagle's two-stage model that he described in his paper seems more related to me:
Eagle, T. 2010. Modeling demand using simple methods: joint discrete/continuous modeling. In Sawtooth Software Conference
Proceedings, pp. 283–308. Orem, Utah: Sawtooth Software.
Essentially, you are building a model of choice first using MNL approaches (like our MBC does). But, then you build a second regression model that relates the utility of the alternative from the first model to the rating scale from your Appeal variable.
Or there are classes of models that I haven't played around with that involve predicting consideration, and then choice given consideration. But, your second stage is a rating, rather than a choice.