I struggled with this too. Priced out buying the perforated stainless (16 gauge 304 stainless) and having friend cut and weld. Was maybe half the cost of Norcal. But my friend would be learning how to make it on my false bottom. I only needed one false bottom and I didnt want a prototype. I bought it from Norcal and it fits my kettle perfectly, and my recirculating mash flows like a champ even with lots of wheat in the grain bill. No scorched grain or wort under the FB.
As for the $30 domed false bottoms I was building direct fire recirculating mash tun in a 15 gallon flat bottom kettle and was concerned about less than 100% coverage of bottom and tendency to move when the mash is stirred, Biggest I could find was 12" (kettle is 15.5") and I don't think the 12" was $30.
Perhaps now that I have the unit from Norcal I will let my friend make a duplicate for my brew kettle if he really wants a metal working project. But am extremely satisfied with the value of Norcal's offering.