If you don't mind my jumping in, I have an idea about "at least". The general idea is that people complain about the cost of nurses. The specific idea is that Mr. Crawley complained about the cost of a particular nurse.
There is a general tendency to use "at least" between a general statement and a specific example that illustrates the generality. The idea of the "at least" is that maybe the general statement is not really universally true, but there is (at least) one example that supports the general statement.
People are stupid. At least my brother is!
Trips by train are horribly uncomfortable. At least my train trip through southern Italy was.
New Yorkers are a rude lot. At least the doorman at the Waldorf was rude to us.
Everyone loves roast beef -- at least everyone in our family.
Nurses are really too highly paid for what they do. At least Mr. Crawley thought so, since he complained about paying for nursing service for his father.