Fixing a problem in development costs 10 times as much as fixing it in design

..And costs 100 times as much after product release. A lack of planning can result in more than just a disrupted timeline – It can have a significant impact on the budget as well. The price difference here is drastic; it comes to a choice between thinking ahead now or throwing money at the problem later in order to achieve the same end goal: a frictionless user experience.

Source:
https://uxplanet.org/why-investing-in-ui-design..