CBS made exactly what they wanted on each and every Blu-ray set of TNG that was sold. They charge wholesalers and huge retailers like Amazon a pre arranged price based on the volume of stock which those wholesalers and retailers are buying. It's the retailers who then stick a 500% mark up, or whatever they think the market will bear, on the sets, which is how most retailers were arriving at $60-70 per TNG set in the US, and £55-60 in the UK.
Now, if those sets suddenly drop to $30 or £25 because the retailers can't shift them at $60, it's the retailers that are losing out, not CBS. CBS has already had its money, although I'll admit that as sales were poor, retailers wouldn't have been buying any more units.
Now, I bet CBS was selling those TNG sets to Amazon for a pittance due to Amazon being the biggest bully in town. That's CBS' own fault entirely. If CBS didn't make enough money on the sets, it's their fault. Not the fault of customers for not buying them. If CBS wanted to shift TNG on Blu and make a decent return, it should've sold direct to customers.