Bought it used (but literally like new, not even a scratch) for €180 and then slapped on it 2x32GB RAM sticks (Patriot, DDR4 3200Mhz, €68 for the two sticks), a 1TB M.2 2280 (WD_BLUE SN570, €54) and a used Intel AX200 Wi-Fi card (€15) for a total of €317 for the laptop + the upgrades (+ this dock as the seller included it with the laptop: https://support.lenovo.com/us/en/solutions/pd500180-thinkpad-hybrid-usb-c-with-usb-a-dock-overview-and-service-parts). I also did a repaste with some Noctua NT-H2 paste I had laying around.
I'm really happy with it right now, and yes the T480 does support 64GB of total RAM despite the official website and even the system itself reporting 32GB as the maximum installable capacity, and yes you can also go for higher frequency sticks as long as they are DDR4 as they'll downclock themselves to the max supported frequency of your laptop anyway, this is important because old DDR4 sticks are rare and expensive.
Great buy and upgrades, btw what is the model number of the RAM sticks? It's actually useful if someone needs to buy compatible RAM.
The sticks I bought were Patriot Memory SODIMM DDR4 3200Mhz sticks. The full details are: DDR4 3200 MHz PC4-25600 32Go (1x32Go) C22 - PSD432G32002S.
Much appreciated! I'm sure those details might help someone in the future.