Dangerous Prototypes Open Source Hardware

My mistake, I thought you were saying $300 for a transformer.  The around $100 was for the parts, not including the transformer.  That's only for one set.  I cannot do it for you, and all I did as far as the parts, was added the parts, or equivalents, from the BOM on github, to the carts, I didn't save any copies, since I didn't end up ordering anything, just telling you my experience.

What transformer are you looking at?  The one I got is still around $50 US.  Either from Mouser or Digikey.

https://www.mouser.com/ProductDetail/Triad-Magnetics/VPT24-6670?qs=wkKrz7WmEgM9dyICyimRcw%3D%3D
https://www.digikey.com/en/products/detail/triad-magnetics/VPT24-6670/2090084

If you have someone build it for you, like JLCPCB, yes it's definitely going to be more expensive.  Keep in mind that when he posted that figure it was in 2015, prices have gone up.  Last I checked, which was a few months ago, the parts will run around $100, then you have the PCBs, but they aren't that expensive, especially if you order them individually.  If you try to order them all panelized (all together), they will cost A LOT more through JLCPCB, because they tack on an extra engineering fee.

Unless you are going to build it yourself, expect it to cost a bit more, depending on who is making it.  It was never meant to be a project that you could just send to a manufacturer and have it built for that cost, it was always a project for someone to do it themselves, to save costs.

There are also a lot of JBC C245 clones out there, though they aren't perfect either, but all you have to do is search for them. 

Around 70-90 EUR per assembled set of PCB-s. It is still pretty lower then original controller from JBC for example.

All parts are available from Farnell - you can check part prices yourself if you want to.