How about sites with paywalls signal this, including subscription price, in a HTTP header (or whatever) to crawler bots? Then Google users would be able to fil

How about sites with paywalls signal this, including subscription price, in a HTTP header (or whatever) to crawler bots? Then Google users would be able to filter by "free results only" or "paid results, less than $x/month". Seems like a relevant search criterion, especially for industry-specific articles (like finance).