For a sub-minute flight the drift budget is actually pretty forgiving — a MEMS gyro drifts maybe 1-3 deg/sec, and if you're fusing with accelerometer data you really just need "which way is up" and "am I still pointed at the target." A $5 IMU can hold that for tens of seconds.

Where you're right is repeatability. Mil-spec works the same on launch 1 and launch 500 across temperature extremes. Consumer MEMS you'd need to characterize each unit individually — fine for a demo, impractical at any scale.

Good $3 MEMS gyros are about 100x better than that now - look at anything new made by Invensense in the past couple years. And their drift is pretty Gaussian-distributed, so the error scales as sqrt(n). If you combine 8+ of them on one board you can get about 5deg/hour stability...

Hm. Is it, though? If what you wanted to do was produce a large batch of calibrated IMUs, building a rig to do so wouldn't be an enormous undertaking.

Or do you mean to characterise the assembled vehicle?