Hi, I am also looking for those kind of APIs as well for my own program. It's quite a "cross-disciplinary" topic.

However, there are quite a few major obstacles:

• All available and possible APIs that I have gone through don't have the ability to search with fare class. You have to find some creative way to achieve that without getting access to raw database. Although there are APIs that return information that include whether this itinerary is basic economy. The keyword you might need here is "unbundled". Sabre, Amadeus, and TravelPort do seem to have options for bundled fare only, but these options might only appear in their entreprise APIs.
• Affiliate APIs ask you for quality traffic with certain conversion rate requirement. Such as Skyscanner, they have a Traffic Quality Score to assess your requests. A lot of affiliate APIs require user IP in your requests. They are also likely to have rules against caching or redistributing fare data. Not sure how strict these affiliate programs are, but the rules are there.
• You are either getting the API for free or paying a much higher price for paid API than $10 a month. It's not gonna get you anywhere with $5 to 10.
• I have the same reserves about scraping. You are making requests everyday instead of a one-time thing. It's quite likely to bump into a rate limit or IP ban. I also doubt the efficiency of scraping and the time it would take to scrap from 5000-10000 requests everyday.
• Many commerical APIs are not accepting individual users/developers. They only accept corporations in the industry.

I have gone through that list before. It seem to contain very few viable APIs that we can use.

It seem hard to find a proper API to use already, not to mention excluding basic economy. Good luck on it.