I agree, soundboards are oddly priced. The Small scale card is quite good but limited. The QSI board does ten times more(it’s also a DCC decoder) for $135. QSI sound is excellent but to get the most out of it you need either DCC or the “quantum engineer” they sell, which triggers the sounds on track power. Phoenix sound quality is excellent and you can trigger a whole range of sounds, but wiring them up can be a pain.
Getting sounds, as Tom says, is the hard part. If you want it to sound good, and not irritating, you need to get more than one sound–you need to get the sounds under different conditions, and you need to seamlessly blend them.
for example with Small scale, the chuff gets faster as the loco speeds up, but it doesn’t sound much different. It’s the same “chuff” sped up. With QSI, the chuff sounds changes as the engine gets under load–faster and slower, but also it changes from loud and labored to quiet and gliding, and it gets a different timbre. It makes the sound much more realistic. To do that, QSI had to record locos under a wide range of conditions and speeds, or else find a way to fake it, which would take a lot of work.
It’s odd to me that a Phoenix card costs so much more than a QSI. The Phoenix sounds are excellent but so are QSI’s and the QSI is also a motor control board that syncs sound to motor load.
MRC makes a sound card for around 50 bucks I think. Have never seen or heard one though
