Rawson Resale......

Couple reasons i suppose... Often people able to recoup what they spent or more. In this hobby change inevitable, no matter how good something may be.
Also, seems about 50% of the things I make go to repeat customers so they might have more than one thing i made and unload the other.

I only dabbled with class D, via Hypex products, for little bit. Cost materials high then like pulling teeth to get above that - not spending 500-550 to beg for 600, just too much liability since there are some gotcha's on them.

Do not have a website... fly just over the trees. Lot of stuff built not my own ingenuity so not out to make notable money on it. Consider it more build for others. In some ways, feel like a non-profit where just administrative overhead as truly better ways for me to make money if that were my motive. If made into business would not be able to make stuff reasonably.

4780 is 2 3886's on chip. typically the 2 parts are paralleled to create more power for low imp loads. though can be bridged to but need to run low rail voltage so stable for various loads. audiosector and tech-diy sell 4780 kits. i don't make 4780's since my boards are for 3886 and some for 1875, definitely need fabbed board for 4780. plus need to electrically insulate from heatsink. in general easy enough for me to just put two 3886 together myself. lastly, find single 3886 works well enough and only need multichip parallel if driving tough load - in which case you might want to consider a different type of amp to begin with.