Microcontrollers with extreme high temperature range
When doing down-hole stuff for oil and gas - my guess is the cost of a chip is not going to make any difference on the economics of your whole project.

You may be spending more money on time wasted looking to save even $100 in parts.

Say you cost $100 per hour (salaries + overhead). Not unreasonable if you are a good engineer.
Say you save $100 by spending 20 hours searching for a cheaper part. That's amazingly good savings on a single microcontroller.
Say you build 100 units per year. That's a lot of units in that industry, even though you may destroy one in every job you do.

Your added engineering cost is 20 x $100 = $2000.
Your saved production cost is 100 x $100 = $10000 per year.

Looks like a great deal, but if your project is valuable to customers. In that industry that means a lot of money. Say $100.000 per job. And say you can do 100 jobs per year.

That's $10M per year.

Now those 20 hours you finished late because you wasted time searching for a cheaper part ends up costing your company 20/(8 x 200) x $10M = $125.000 (if and if and if... I, know - but you get the idea).

My short answer: Stop searching when you have found something that works well. Unless you are making 1K-10K units per year or more... Build it and start making money instead of blindly focusing on BOM cost.