To determine which option is less expensive, we need to compare the cost of ordering contact lenses for a year's supply at once versus ordering them for a month's supply and repeating this 12 times.
The cost of ordering a year's supply at once is $300.
The cost of ordering a month's supply 12 times is $30 x 12 = $<<30*12=360>>360.
Therefore, it is less expensive to order contact lenses per year, paying for 12 months at one time.