Go the federal budget route, round down until you get to "in thousands" or "in millions" for everything. Then it's still easy to compare $12 to $36,000 at a glance without staring at a table full of 000,000.00 :)
It's about information entropy, you want to maximize the information each character has. using 1000 digits to show what you could in 500 and a header saying "(in thousands)" maximizes the entropy