Yes I have 2 "Titanium S-Joy Converter PS to USB PC Controller Adapter" and they work perfectly with MAME and every other emulator that support,s controller. MKT PC Version works perfectly too.
After you installed the drivers for the adapter, Windows will handle the PSX gamepad like a normal PC Pad and you can play everything with that.

I have one that I bought at radio shack. It works like a dream. I have my PC hooked up to my TV, compined with a new menu system, like MAMEWAH, and the cordless logitech PS2 controller, it's heaven.

how much it cost?

Adapters cost anywhere from $10 - $15, I have been through tons of them, along with a friend, trying to find one that works with everything (as in OS, controller types) and nothing seems to. One will work in XP wit only dual shock, and not in Win2K, one works in Win2K with everything, but not XP at all, one works in Win2K and XP with PS1, and not dualshock, I have one controller that works with PS1 on XP and not dual shock as well, but no adapter that work on both systems, with both controller types.

Matt