This is ridiculous. Video doesn't increases the cost of cameras, it reduces it.
Cameras are a mass produced object. It's not like your 5DIII is being handcrafted and each feature must be individually installed. It's a mass production item.
Let me explain. Manufacturer "A" makes $100 profit on each unit they sell of Product "B." They have a goal of $10,000 profit. They sell 100 units, they make $10,000. But, if they add feature "C" to the product, it will reduce their per unit profits by $10.
But at the same time, they know that adding feature "C" will boost their sales by 30%, so when they sell Product "B" at $90 profit, they actually net $11,700, exceeding their sales goal. So, instead of selling Product "B" at $90 profit, because they have increased their sales volume, they decide to cut the price by $3 and sell it at $87 profit. The company still surpasses their sales goals and consumers get a product at less cost, but with more features.
As long as the ratio between the increased sales due to video exceeds the marginal cost of including the feature, the per unit cost (which is what we consumers should be concerned with) is actually lower with video than without. This is what is called the "industrial revolution" and it happened about 150 years ago.