Go to your local carpet shops, when i went to my local the guy there said he was selling more of it than carpets!
You can get a good feel for it, and all my shops were similar prices to online.
I used a spade and dug about 6"-8" of soil out, added some drainage and stones and then the new "carpet" over the top.
One thing i wish i did was let the stones settle for 2-3 months, they did drop down at least 1-2 inches when they settled and it doesnt look as good as it did when it was first laid.
You can get a good feel for it, and all my shops were similar prices to online.
I used a spade and dug about 6"-8" of soil out, added some drainage and stones and then the new "carpet" over the top.
One thing i wish i did was let the stones settle for 2-3 months, they did drop down at least 1-2 inches when they settled and it doesnt look as good as it did when it was first laid.