Is there any financial impact of design failures?

Yes I 100% believe so, but it is very hard to measure. Your potential customers will most likely never say that the reason they chose not to buy was the design, but it will likely have had an impact on their decision

Yes, for sure. Use testing to find the best result.

Absolutely. Besides bad designs being off-putting to customers there is also a science behind checkout flows and button placements that lead to higher or lower conversion rates which directly translate to profit/cost.

There 100% is, because first impressions are EVERYTHING. Have you ever used a new product, gone to a new store/restaurant, or visited a new website where the initial experience was less than desirable? Did you have any interest in going back or giving it a second chance? What about the opposite, where the initial experience was amazing? Design is the same. If your design is poor, be it UX/UI, visual, etc., you're leaving a poor first impression, and that can absolutely impact whether or not you land a sale or retain users. Additionally, there are a lot of specific design choices that can drive more conversions for you. There's a reason why so many companies do A/B testing when it comes to advertising or marketing or user testing. Design choices will always have some kind of impact on the user, and that impact will inevitably be linked to cost.

Yes, bad designs = bad development = bad UX. But the cost of hiring qualified designers is high. That's why we offer our services, because many startups don't want to incur the costs.