Our brains are hard-wired to believe the size of the item represents its value.
It means it cannot easily distinguish between visual size and numerical size.
So, if you display your prices in smaller font size, they will be perceived as being smaller in value.
Another way to achieve the same effect is to position large texts and other elements next to the price. The price will look smaller visually in comparison which will translate in them being understood as being smaller in value.