CCI parts are expensive, So are the other name-brand valve company's parts.  That's because the manufacturer has to develop the part, maintain engineering records, material controls,ISO9000 programs, Manufacturer's warranty, and assume legal responsibility for the parts. And yes, the stockholders expect a profit. The valve maufacturer probably had to discount the valve down to around cost to sell it to you in the first place, and parts sales is probably the only way he will ever make any money on the gate valve.  
If you start swapping out OEM parts with parts that you get from the back of somebody's Pontiac that look sorta like the OEM parts: They MAY have the same dimensions, and they MAY have the same materials and they MAY have the factory spec heat treatment, and they MAY have used the factory spec weld procedures, and they MAY have the factory spec surface treatment, but that ain't the way to bet.  If you have a name-brand valve that's giving you trouble, and the factory service tech comes in and finds pirate parts in it, you're going to lose the warranty on every valve on your site, if not in your whole corporation.
You used the example of CCI valves.  I will admit I have NEVER heard ANYBODY talk about how well he was treated in dealing with them, but the reason anybody buys a CCI valve is for a CRITICAL SERVICE.  Failure of a critical service valve can result in property damage, injury, massive and prolonged economic damage to the facility, or even death.

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