Monthly cost or $10, whichever is less, is better. It means the landlord is incentivized to keep costs down. Even if it costs the landlord $50, they can only charge the tenant $10. If it costs them $5, they can only charge the tenant $5. It’s a ceiling on the cost.
I assume the landlord uses a service to share rent with the credit report agencies. The landlord can shop around for a cheaper service, or use their cousin who charges $50/tenant but gives the landlord a kickback.