Historically, Arabic fonts suffered on digital screens because their internal spaces (counters) would fill with ink or pixels. Expo Arabic counters that (pun intended) with extremely open counters and a large x-height.
Note: Many versions also include a axis, allowing designers to fine-tune the weight and width dynamically. Expo Arabic Font Family
A full family (9 weights) web license can range from $150 to $500+ per year depending on traffic. A perpetual desktop license may cost $500-$1,000. This is an investment in quality. Expo Arabic Font Family