Identifying members who are likely to move to a lower cost alternative product
We could analyze the customer's purchase history. Here, for the sake of explanation let's assume that customers A and B. First, we'll make the purchase history of customer A,


We'll calculate the frequency of customer A buying the mid-range pan. Also, we'll need the total number of purchases made by the customer. So, for customer A you'll get a ratio which is ( number of purchases of the mid-range pan ) / total purchases.
Similarly, we'll calculate such ratios for the expensive pans both for customers A and B.
Next, we'll compare the ratios for all customers and select the highest N customers who most probably will buy the mid-range or expensive pan.


Why are using the ratios ( or precisely, the probabilities of buying a certain pan )?


We'll need customers who are frequent buyers of a particular pan. These are more chances of switching a product rather than the less frequent customers.
As they are regular customers, they will be more influenced by the discount available on the mid-range pan.



  You may use various metrics to aggregate the customers who can have a product transition. You may also have a look at Bayes Theorem which I think will be appropriate too. It will give the answer- "Which are customers which have the highest probability of buying a mid-range pan given that they have already bought a expensive pan.