Does knowing that 1% of people own 99% of the wealth affect your marketing strategies, pricing, etc?

I don't have any source to give you an exact answer right now, but:

20th Nov 2017: The average American household carries $137,063 in debt, according to the Federal Reserve. The U.S. Census Bureau reports that the median household income was just $59,039 last year.

22nd May 2017: The median student loan debt for a person who has attended some college or graduated from college is more than $49,000. The average household credit card debt is about $5,000 with the median debt at more than $16,000. The average mortgage debt is nearly $173,000. The average auto loan exceeds $30,000. Personal loans and other miscellaneous debt are more than $10,000 per household. The total average of debt combined (including those who have no debt at all) is $139.5 thousand per household.

Net worth calculator from 2017 (including primary home): A $0.00 net worth was percentile 11% in 2016. This wealth percentile contained around 629,908 US Households and ranged from $0.00 to $1.54. We estimate around 112,123,713 households had $0.00 or more in wealth.

Although the last one is the closest to being an answer, I've heard numbers in the past that were higher, but that's anecdotal so feel free to ignore it.

if there are examples of ignoring the rest and focusing on 10%

That's what happens if you target a first world country. Or sell online and assume your target client will have:

1. Any type of computer (including smartphones etc.).
2. Electricity to waste.
3. Internet access.
4. A need for any virtual project (e.g. CRM/SaaS/...) to improve their lives instead of food, water, clothes or housing.
5. Disposable income.

10% of the world is ~765 million people. For reference, the US has a population of ~325M people.

There are at least ~60 countries in the world (out of ~176 w/ stats on this source, so 34%) where the average wage is below $500 (and the average is a bad statistic because of corruption and income inequality), so paying for a $99/mo SaaS isn't going to happen.