I prefer to quote per project rather than per hour for my web scraping work because it:
- gives me incentive to increase my efficiency (by improving my infrastructure)
- gives the client security about the total cost
- avoids distrust about the number of hours actually worked
- makes me look more competitive compared to the hourly rates available in Asia and Eastern Europe
- is difficult to track time fairly when working on two or more projects simultaneously
- is easy to estimate complexity based on past experience, atleast compared to building websites
- involves less administration