Well, the way I figure it is that countries are only buying J7s because it's the cheapest thing on the market, especially in terms of new builds.
Take that option away, and the JF17 suddenly becomes a great deal more attractive.
All other considerations that make the J7 attractive, like no strings attached, able to use commodities to part finance the deal or great financing options offered by China would still hold true for the JF17.
If someone really really doesn't want anything fancy, well they can choose not be buy any BVR missiles, and I am sure CAC could be persuaded to stick a J7's radar into the nose of the JF17 is the customer is that strapped for cash. But I really doubt it will come to that kind of penny pinching.
I am sure the air force generals and pilots would love to have JF17s to play with as opposed to J7s. By taking J7s off the table, you are strengthening the hand of the air force in bargaining for JF17s from their governments.
Maybe I am underestimating the complexity of these deals, hell, I hope I am, because I would like to think the people at CAC have as much business acumen as they do engineering skills.