Builtwith.com (one employee/founder and a part-time blogger) does an estimated $12M a year [1] assuming a 'few thousand' = 2000 paying customers.
"the Basic at $299 per month for customers that want lists of sites mainly for the purpose of lead generation; Pro at $495 per month, suited more for users that work in an industry using a lot of A/B testing and comparison-type data; and Enterprise at $995 per month, which covers all bases and allows sales teams with multiple people to all use the platform at once. Brewer says that in terms of paying users on the platform there is a ‘few thousand’ and the split is about 40 percent Basic, 40 percent Pro and 20 percent Enterprise."
"the Basic at $299 per month for customers that want lists of sites mainly for the purpose of lead generation; Pro at $495 per month, suited more for users that work in an industry using a lot of A/B testing and comparison-type data; and Enterprise at $995 per month, which covers all bases and allows sales teams with multiple people to all use the platform at once. Brewer says that in terms of paying users on the platform there is a ‘few thousand’ and the split is about 40 percent Basic, 40 percent Pro and 20 percent Enterprise."
Similar thread a while ago [2]
1: http://www.startupdaily.net/2015/09/builtwith-is-perhaps-one...
2: https://news.ycombinator.com/item?id=12065355
Edit: specificity and formatting