I think that salary was when they were still working for ted healy (who was getting paid 5 thousand a week). When they started filming their shorts at columbia (without healy), they were paid a thousand a week (which they had to split 3 ways). Over time that would be increased to 7500 a week.
Although their salaries were modest for the films they produced, they made much more during the year playing nightclubs and other venues. Offstage, Moe was sensibkle and conservative when it came to money. Larry was a heavy gambler, and Curly spent most of his money on women and booze. Because of this, Moe talked the other two into giving him part of their salary each month so he could invest it for them. He knew that one day their show business career would be over, and wanted them to have money to live on when that day arrived. As for Moe, he made a fortune in real estate.