One-time Registration Fees. There is a $4 fee to register your local number, regardless of your plan.
Monthly Subscription Fees: There is a monthly fee of $10 to maintain your number with mobile carriers.
Annual Vetting Fees: If you require a larger messaging volume or higher throughput, you will need to go through a vetting process. The standard vetting cost is $40 per year. This fee is due upfront at the time of registration.
*Based on your vetting score, you could have up to 200,000 messages per day for T-Mobile customers (other carriers do not have a limit at this time).
You can learn more about registered local numbers or 10DLC here.