In the end I'd be thrilled if I could get the parts individually like you did and make the same product for under a grand.
Oh you definetly can. My BCS is crazy over build with lots of additional stuff and I came in at around a grand for a panel that would have probably ended up costing over $3000
I had to source a few things from retailers, but most were small items. I couldn't find the proper 50a contactor for a din rail off eBay, so I ordered it. I also had some other small things I had to find from other sites other than eBay, like the heat sink. But I got that from another company who makes them.
But all said and done, my SSRs are all brand name (crydom) my plugs are all brand name and the proper flanged ones. Like I got the 50a plug for $18 and the 15a ones (all 4 for $20) the 50a one is probably $50-75 retail while the 15a ones are probably $25-30ish ea
I also got stainless steel float switches for the side of the tank. They're just like the ones a retailer sells for $40/ea. They cost less than $10/ea if I remember. I bought 3 of them.
I built all my temp probes. I bought the sensors and the SS tubes from brewers hardware along with the BCS 462 controller. I couldn't source those any better and the quality is top.
I bought 100ft of mic wire for a few bucks on eBay (free ship) and built my own sensors with 10ft cables. They work awesome and cost a fraction of the price. I found a reseller on eBay who sells the 1/4" compression to 1/2" pipe for something like $15 shipped for 5 of them I think. It was really cheap.
Anyway, I didn't cut any corners on my build. I in fact upgraded majorly. But it was a lot of work and took a lot of time to find the parts. I just waited until I found the right deal for each thing. And then there's the assembling of it... But it's part of the fun.
Oh, and I have Amazon prime (free shipping on prime orders) I get 99% of my stainless steel fittings off Amazon. A $5 (plus shipping) item from a brew shop costs $1 on Amazon with free shipping. (eBay is another good source of that kind of thing. I always search for free shipping)