We examined the expectation of customers randomly regarding the price. 85% of survey respondents evaluated the product highly. While we have to raise the cost because persistent extremely high material prices. bu doğru görünüyor mu?

In the first sentence, I would change "examined" to "surveyed" because examined sounds like you're testing them rather than asking for their opinion. I would also change the position of "random" in the first sentence to:
We randomly surveyed the expectation of customers regarding the price (of the product).
Or
We surveyed the expectations of random customers regarding the price (of the product).

I think the second sentence is a little weird because of the context.
If you mean the customers though the price was high/expensive, I would change the second sentence to:
85% of the (survey) respondents thought the product was (too) expensive.
or
85% of the (survey) respondents thought the price was too high.

For the third sentence, I would change "while (~하는 동안)" to "but (~하지만)." I also think you need to take out either "persistent" or "extremely" they don't work well together in this case:
But we have to raise the cost because of persistently high material prices. (값이 계속 올리다라는 뜻)
or
But we have to raise the cost because of extremely high material prices. (값이 너무 비싸다라는 뜻)