What would be a string to replace:

This is $1.00. Ain't that nice
$1.00 for this stuff.
Buy this now for $1.00

with the format:

$1.00 {rest of the stuff from string}
so the output would be.
$1.00 This is . Ain't that nice
$1.00 for this stuff.
$1.00 Buy this now for

This replace regexp will capture everything before and after the string you care about, and change places of the found groups in the required order: 
s/(.+)(\$\d+\.\d\d)(.*)/$2 $1 $3/g