It's a tough one. I've made the site 100% free in the past and got hit with a ton of SEO service and web development spam. Had to set up a paywall to increase the quality of buyers.

Also, a lot of data that sellers provide is sensitive and they don't feel comfortable with everyone having access to financial data, traffic etc. as competitors can abuse this information.

I send out around 2-5 startups every week with free access to newsletter subscribers (have a bit more control) hence the prompt to subscribe. This really helps regular subscribers with the kind of startups listed on the marketplace.

Also made the top 3 free to view now, hope this makes for a better user experience.