Originally Posted by akatona
You are missing the point completely. To rephrase: it does require expertise but it doesn't require you to have one if you can have it made for you. Do you think there are that many manufacturers that make ICs?
opamps are cheap, because the technology is outdated and has paid for itself, however it still costs a fair bit of money just to get the factory to start the process and it takes weeks to get back a sample, if at all. If you tried to go out and pay someone to make an IC, it would cost tens of thousands to get back a sample for debugging.
Buying off the shelf ICs is another story. They are cheap because they sell in the thousands and the initial outlay can be repaid pretty quickly.