When considering the salary for their staff, it is important to point out that LetsEncrypt only works if there is trust. They need to have high caliber people that they can trust and this costs money. Hearing that LE Is paying their people a fairly good wage, makes me much more comfortable using and supporting them.
Lots of people are talking about how expensive Silicon Valley is and how they have to compete with other salaries... but this is the justifying reason to me. If you pay enough that money is off the table, you can trust them a lot better.