Cal. Civ. Proc. Code § 2034.470

(a) If a party desiring to take the deposition of an expert witness under this article deems that the hourly or daily fee of that expert for providing deposition testimony is unreasonable, that party may move for an order setting the compensation of that expert. Notice of this motion shall also be given to the expert.
(b) A motion under subdivision (a) shall be accompanied by a meet and confer declaration under Section 2016.040. In any attempt at an informal resolution under Section 2016.040, either the party or the expert shall provide the other with all of the following:
1. (1) Proof of the ordinary and customary fee actually charged and received by that expert for similar services provided outside the subject litigation.
2. (2) The total number of times the presently demanded fee has ever been charged and received by that expert.
3. (3) The frequency and regularity with which the presently demanded fee has been charged and received by that expert within the two-year period preceding the hearing on the motion.
(c) In addition to any other facts or evidence, the expert or the party designating the expert shall provide, and the court’s determination as to the reasonableness of the fee shall be based on, proof of the ordinary and customary fee actually charged and received by that expert for similar services provided outside the subject litigation.
(d) In an action filed after January 1, 1994, the expert or the party designating the expert shall also provide, and the court’s determination as to the reasonableness of the fee shall also be based on, both of the following:
1. (1) The total number of times the presently demanded fee has ever been charged and received by that expert.
2. (2) The frequency and regularity with which the presently demanded fee has been charged and received by that expert within the two-year period preceding the hearing on the motion.
(e) The court may also consider the ordinary and customary fees charged by similar experts for similar services within the relevant community and any other factors the court deems necessary or appropriate to make its determination.
(f) Upon a determination that the fee demanded by that expert is unreasonable, and based upon the evidence and factors considered, the court shall set the fee of the expert providing testimony.
(g) The court shall impose a monetary sanction under Chapter 7 (commencing with Section 2023.010) against any party, person, or attorney who unsuccessfully makes or opposes a motion to set the expert witness fee, unless it finds that the one subject to the sanction acted with substantial justification or that other circumstances make the imposition of the sanction unjust.