Hard to say the value on anything anymore since it varies so much depending on the marketplace. Personally I'd think $140-175 range with cables/controller for a one-off of someone selling an extra Saturn they have laying around on a forum (no fees) with a modchip (which costs 20-40 USD depending on the source). Region free BIOS is nice, but if you're playing CD-Rs just patch the image before burning to save money. This is USA by the way, but hopefully it helps.
Thanks for responding. I just ended up getting a 'Pseudo Saturn V6.314 1M 4M All in one 8M' for £33. I already have a stock white Japanese Saturn doing nothing in a cupboard so I'll just install a Pico PSU in that so it's usable without any step-down and use the Psuedo cart.