Legal Question in Civil Litigation in California

Chump change. $35/day and $0.20/mile.

I'm assuming you are referring to a subpoena for a deposition, and not a deposition subpoena for records production only. If you are testifying as a percipient witness, the rate is $35 per day and 20 cents per mile, for mileage actually travelled, in both directions (to and from.)

This answer assumes that you are not a peace officer. There are special rules for peace officers subpoenaed for deposition.

If you were testifying as an expert, and were properly designated, you would be entitled to charge your reasonable and cutomary hourly or daily fee.