“Each quarterly price reduction will take effect Day 10 of a new quarter of Quarter beginning with the start of the first full quarter
You might use:
“Quarterly price reductions shall commence on July 10, 2007 and shall be applied each January10th, April 10th , July 10, and October 10th of the term.
(The difference is in the first day 10 could be measured as either business or calendar days whereas in the second makes it a specific date.
The Price shall be forty-six dollars (US$46.00).