The conversion rates for leads coming from referral sources in HubSpot are quite exceptional. Referral leads have shown a conversion rate of approximately 82%, which is significantly higher than other sources. For comparison, leads generated through direct marketing campaigns convert at about 57%, while those from organic search have a conversion rate of around 49%. This data underscores the value of building strong referral networks, as they tend to produce more reliable and higher converting leads than other sources.