Pretty much.
Samsung has a business model. Their goal as a business is to earn a certain % of profit on every unit sold.
They probably through their internal budgeting have stated a minimum pricepoint in which they can sell their panels and still maintain their percentage according to budget.
Apple comes along and tells samsung "if you dont sell me that panel at X, we're going elsewhere".
samsung does the math and sees that at that price, they still maintain the percentage of profit needed and agrees.
fast forward a few years later and contract is up for negotiation. Samsung budgets again and sets their pricepoint to maintain profitibility.
Apple comes back, and demands yet a new lower price. Says "we're apple, we buy 15 mil pannels, take what we offer or leave it"
if this new offer doesn't cover the budgeted revenue levels, and is even low enough to possibly remove profit completely, Why would Samsung agree? they're not in business to be a charity house to Apple. Samsung would firmly believe that they can find suitable sales elsewhere for those 15 million, that maintains their budgetted values without having to compromise possible profits and revenues.
this decision likely wasn't personal as everyone wants to believe, but can likely be found to be purely accounting.
I hate accounting