There is no extra cost to you when using an Amazon (Hub) Locker.
The following applies;
Standard shipping and free shipping may be unavailable at some Lockers. Same-day delivery and one-day shipping are available in select areas only. Free two-day shipping is available for Amazon Prime members. Standard shipping rates apply for all other orders.
An individual cannot buy a Locker. Amazon owns the Lockers and subleases space (for a nominal amount) in a commercial establishment. They also save costs associated with every package delivered to a commercial location.