Bricks, Masonry, Asphalt and Concrete - Crawl space excavation

I own a 1939 Frame house on a raised foundation. The crawl space, however, is extremely messed up. It was originally very shallow, certainly less than 18". To get around down there, workers in the past (before I owned the house) dug trenches to navigate to the various areas they needed to work. But instead of removing the soil, they simply pushed it to the other side of the piers, making access to the other areas of the crawl space impossible. (A plumber I brought in to give an estimate on copper re-piping said he wouldn't consider doing the job until I excavated the crawl space).
So I brought in a foundation contractor to give a bid on excavating the crawlspace to the required 18". His estimate was $6500.00 and he estimated there was 30-35 cu. yds of soil to be removed. In addition, the center piers would need to be replaced , with new footings, pier blocks and new, longer 4x4 posts. There are 15 piers to be replaced. That cost was an additional $5500.00
So this job would cost $11,000. I thought that was extremely high, but a second bid was $13,800.00.
The first contractor said he would lower the price to $7500.00 if new footings were not poured, but the the pier blocks were just set 6" into the hard packed soil. Something about that sounded a bit dicey, especially since we are in earthquake country. (Southern California/Los Angeles)
Do these bids sound accurate? Am I right being wary of omitting the footings?
Both contractors said the perimeter foundation was very solid, especially considering the age of the house, and the soil was extremely hard packed, which was good for the foundation, but bad for excavating.
Any advice would be very helpful.

Have you considered raising your house & installing new steps & skirting in lieu of excavation.

It was suggested by a relative, but half the house (more recent additions) are on a slab. It wouldn't work.
Oh, the original 1939 house on a raised foundation is 850 sq. ft. The additions are about the same, 850-900 sq. ft. (slab).

If there are no wires, pipes, etc. to deal with, you may be better off getting some teenagers needing some spending money & supervising them to excavate between the rows of piers. Rebidding after the excavation may lower the costs of the contractor bids.

Unfortunately, there is everything: Gas, electrical, water, sewer. Thanks for the tip, though.