The cost of Conversion Rate Optimization (CRO) services varies widely depending on factors like CRO agency expertise, project complexity, and service scope. Also, website size, testing frequency and usage of complex tools can impact pricing. Top-tier agencies may charge anywhere between $10,000 to $30,000 per month. Mid-tier firm prices may range from $6,000 to $8,000. Low-tier agencies or freelancers might charge from $2,000 to $5,000.  Do note that the range stated may vary. It is important to assess your specific needs and budget constraints to choose a service level that aligns with your goals.