10DLC throughput is determined by the carriers, based on your Brand Vetting Score as well as the type of campaign, not on the amount of numbers/10DLCs associated with a campaign.
The table below explains how AT&T and T-Mobile/Sprint define each message tier and map Brand vetting scores:
Note:Verizon is still working on defining its process.
Carriers require a ‘special business review’ request; in case a brand is not satisfied with the defined TPM or message daily quota allotment. T-Mobile/Sprint charge $5,000 USD to submit a ‘special business review’ request specifically to increase your daily volume. This fee is non-refundable, but is currently waived.