In Califonia cause of the ST Andreys fault line where the PACIFIC PLATE and the NORTH AMERICAN PLATE slide pass each other.
Thus, my ballpark estimated cost (basically for the AT&T conference call, $50 witness fee, $150 process server's fee; $400 deposition transcript, $25 for copying costs, and about 10 hours of legal work amount to a grand estimated total of about $625 plus 10 hours of legal work.
According to FRCP Rule 30, the number of depositions is limited to 10 depositions per side (i.e. plaintiffs and defendants), with deposition of each deponent limited to 1 day of 7 hours (unless specified otherwise in Local Rules of the District).