The cost of services provided to a charity can only be deducted for charitable contributions, not the value of the services themselves.

Deductibility does not apply to the value of your time or services. Your time can't be deducted if you volunteer at a food bank or provide professional services, such as legal or consulting work.

However, you can deduct expenses you incur while providing services to a charity. For instance:
The IRS standard mileage rate applies to the mileage driven for volunteer work; Materials or supplies purchased for the charity; Travel expenses associated with volunteering (like lodging or meals, if the charity activity is specific).

Here is a demonstration for the explanation:

A public nonprofit elementary school is being supported by Sophie, who is a talented musician who performs for free in a benefit concert. She charges $500 for her services, and she spends $25 on parking and tolls to get to the venue. These expenses are not covered by any reimbursement. What is Sophie's charitable contribution that can be deducted for the year?

Despite there being no deduction for services contributed to a charity, Sophie has the option to deduct unreimbursed expenses related to her donation. As a result, Sophie can only deduct $25.