I'm pretty new to hardware stuff. I have a basic idea to build a hardware controller for some proprietary software. I would need to read about 60 analog faders/potentiometers and 30 buttons. Also I need to drive about 40 LEds. I have Arduino or Raspberry Pi at hand. Up to 60ms delay from mechanical movement to registered value would be ok. I found some digital potentiometer accessible via I2C but at a hefty price (14$ per piece - I'd need about 60 of them)
Look for multi-channel ADCs to read your pots, chips with 16 or 32 channels are not unheard of. Or use analog muxes as Colin suggested, here's a DIY friendly solution if you're planning to solder by hand.
For buttons and LEDs, you can use multiplexing or shift registers, as described e.g. here.