A price reduction for a product shown as "$X off" or "Save over $X", implies that the saving is off the "normal selling price" or the recommended retail price (RRP) on the basis that the "normal selling price" or RRP can be regarded as the usual price for that product.

If you are challenged about the price reduction claim you would need to demonstrate that you had either sold a number of items at the higher price or at least had them offered for sale at the higher price for a "reasonable" period.

The number of items sold or the length of a "reasonable" sale period will depend on the type of items offered for sale.

If there is no RRP for the goods being sold, it is misleading for an advertisement to claim that there is one.