I'm sorry I've forgotten who asked this.
Re arbitration and mediation. I had to look this up so YMMV -
Looks like it varies in terms of who pays for an arbitrator. In
Chavarria v. Ralphs Grocery Co., No. 11-56673, 2013 WL 5779332 (9th Cir. Oct. 28, 2013), the plaintiff was forced into arbitration and the US Court of Appeals for the Ninth Circuit (that's Federal court, sports fans) found the employer had to pay for it (they didn't like her labor contract, either). But this was based on California state law requiring an employer pay for arbitration.
Harris Kaufman, in what looks to be general information on their
attorney Matthew A. Kaufman's page says in an arbitration, a client may be required to pay a portion of the arbitrator's fee.
As for mediation, per a website called
Free Advice (I can't vouch for their accuracy or whether their information is at all up date), it seems the parties chip in.
As for whether one or the other is binding, it appears there is a movement afoot to split the difference and create, you guessed it,
binding mediation. The cited article is from 2012; I'm not sure if binding mediation is a thing yet in California. Note:
it might not be.
Just as a general statement, most states have horrible trial backlogs, so alternative dispute resolution is often encouraged. Doesn't mean it will happen here, but if this matter is settled, it may be via one of these creative alternative methodologies.