Don't people pay attention anymore when buying hardware for AI?

I was trying to sell my old AM4 system, X470 / Ryzen 5 5600 / 64GB / RX580 / 1TB NVME and it didn't sell. Granted it was a bit pricey at 750€, because I took into account the current local RAM and NVME pricing. (Buying the same RAM and SSD new costs 775€ if you go to the cheapest sellers in my country) I decided to try and sell it as an AI system: removed the RX580, put in 2 of my 4 R9700. I set the system up with Fedora to run Qwen3.6 (latest release at the time) and ComfyUI; to show it working. It sold almost instantly! I priced it based on new prices for all of the DDR4 memory, PCI-E 4.0 ssd, both R9700s. I added another 150 euro for the other parts. Total price 5400€! I have since bought back two brand new R9700 from abroad for 250€ less per card than I had sold my old ones for! Effectively I ended up selling the original system for 1300€ instead of the 750€ I originally asked for. Except now I still have the RX580 and fresh warranty on the R9700s. tl;dr know the market for (used) parts before you buy a complete PC for local AI!