Turns out that decking wood is incredibly expensive. 2"x6" cedar decking costs $2.06 per linear foot (i.e., $4.12 per square foot). And that hurts!
I've seen old water tower staves for sale at BIG NYC for $2 per linear foot in the 5" width and $3 per linear foot in 6" width and up in price from there. They appear to be lovely on the inside after just a little planing. But the price is still prohibitive. So, anyway, I found a guy across the river on Craigslist and he will sell me 6'-10' lengths of yellow cedar from water towers in widths ranging from 5" to 9" for under $1.50 per linear foot.
He has both red and yellow cedar and it is all over 20 years old so it seems likely it is older growth than what we get now and may be tighter and a better quality.
Here is a pic of a nice planed piece of the red and a chip of the yellow.
I am probably going to take all his 9 and 10 foot lengths, which add up to about 265 square feet. And that should be enough to re-do the lower deck so that we can roll the hot tub down and hook it up.
Oh, how I long for the hot tub to be bubbling.