Edit: 300/day is too much, apparently I use about 100/day according to my search history.
The person who is willing to pay for a search engine is also going to be a person care more about search and use it more. My best guess is that 1000 searches per month is right on the edge of what their average user can get by with. It's fair enough, they do need to make money, and I have no problems believe that 300 is about right for the average internet user. It just gives a false impression of your expected cost as a potential customer.