Imagine you are about to launch a deal event for your products or services. You create advertisements and design sale signs in your store.
The deal price is a real bargain, but you wonder how you could best bring home the message of a good deal:
How should you present the regular selling price vis-a-vis the reduced sale price?
We will find out today.

Academic research unearths five insights that guide the visual design of your strike-through price.
Insight 1: Do not use fancy fonts for the sale price (just plain, fluent fonts like Arial).
The less mental energy customer need to invest to process information about regular and selling prices, the higher is the perceived difference. Fancy fonts require more mental energy for processing and, therefore, reduce the perception of savings.

Insight 2: Present the regular price with a larger font size than the smaller promotional price.
If the visual price information is congruent to the price level, customer need to invest less energy and perceive the distance between the regular and promotional price as larger - the so-called "congruency effect."

Insight 3: Add physical distance (i.e., white space) between the reference price and the sale price.
Another "congruent" visual cue, is to subtly stress the message of a large distance between the regular and sale price, by increasing the physical distance in the visual.

Insight 4: Present the larger selling price above (if vertically ordered) or left (if horizontally ordered) to the lower sale price.
People can more easily (i.e., with less mental energy) process subtraction when the higher number comes first, and the smaller smaller comes second. The so-called "subtraction effect" explains why people perceive a larger price distance if the higher number is above (vertical order) or to the left (horizontally ordered).

Insight 5: Use red ink in sales prices.
In particular men (who are a bit more conservative with the mental energy - a euphemism for "a bit lazy" 🙂 ), rely on visual cues as heuristics. When sale prices are presented in red, men perceive them as much lower and savings as higher (at least for low-involvement products). For women, a red color for the sale prices has no effect (neither positive nor negative) on the attractiveness of the sale prices.

What did we learn today?
You might have to double-check your price presentation if your current design leans towards the left.

References
Mead, James A. and David M. Hardesty (2018), “Price font disfluency. Anchoring effects on future price expectations,” Journal of Retailing, 94 (1), 102–112.
Coulter, Keith S. and Robin A. Coulter (2005), “Size does matter: The effects of magnitude representation congruency on price perceptions and purchase likelihood,” Journal of Consumer Psychology, 15 (1), 64–76.
Coulter, Keith S. and Patricia A. Norberg (2009), “The effects of physical distance between regular and sale prices on numerical difference perceptions,” Journal of Consumer Psychology, 19 (2), 144–157.
Biswas, Abhijit, Sandeep Bhowmick, Abhijit Guha, and Dhruv Grewal (2013), “Consumer evaluations of sale prices: role of the subtraction principle,” Journal of Marketing, 77 (4), 49–66.
Puccinelli, Nancy M., Rajesh Chandrashekaran, Dhruv Grewal, and Rajneesh Suri (2013), “Are men seduced by red? The effect of red versus black prices on price perceptions,” Journal of Retailing, 89 (2), 115–125.