social characteristics of the researchers and those being researched, e.g.
age profile
ethnicity
social class
cost: if financial resources are low, they may not be able to afford to employ interviewers. also some factors influencing the cost:
salaries
living expenses
travel
computer resources
rent for offices
time - a large budget extends the time available as it includes a sample of thousands of people, therefore, it may take months to process and collate the data
subjectmatter - some areas of social life are more accessible to researchers than others. However, some subject matter is extremely sensitive and difficult to research.