Their website has a contact email. Send them an email as if your were a GC (general contractor) trying to put together a quote using a quantity similar or larger than you need. Ask them to quote it with no shipping as you will be sending a 14 yard truck. Be sure and give them dates and times that you will be needing material. If they don't respond you probably don't want to do business with them anyway. Their number (price) will serve as a benchmark, it will give you a good idea of your cost at any rate.
I guess lava rock is pretty light weight, so you may be able to get a decent price from Colorado, if you buy a large quantity.
Maybe when your neighbors see what you've done you can sell them what's left of the pile, seeing how it's so hard to acquire in those parts. I understand it makes better mulch (keeps the ground cooler and more moist than wood) than wood chips, and doesn't attract as many pests.