Great effort.
As a individual developer, How does using Bing results work? Can I signup for their search engine API and modify them based on my secret sauce, without raking up 100$+ bill every month?
The bill will be based on your usage. For Bing API it is $7 per 1,000 queries for full results (news/video/images). So just raw results without any other effort will cost you about $7/mo assuming you do 30 queries/day.
…and you are not allowed to cache results - so you actually have to call the api everytime you do a search.