Q: AWS Requests Number - S3, Glacier Requests are data operations within storage, e.g. copying data or adding new objects. As a rule, all requests are paid except commands for data deletion.
in AWS S3, requests costs are based the request type. Cloud providers usually charge for 1,000 and 10,000 request packs.
However my question is not really cost related. 
Is the number of requests is actually related to the number of files we applied these operations on ? or does that change depending on the file size we're operating ?

A: Documentation says clearly pricing is done based on per call for each HTTP verb,
https://aws.amazon.com/s3/pricing/
It is not based on the number of files. It is based on number of HTTP requests you make. When you make a PUT call, for whatever the response code you receive back it does not matter. Your request will be counted.
If there is an Outage to S3 and you make a call and if AWS did not honor your call, you can request for "Service Credit" based on the SLA.
https://aws.amazon.com/ec2/sla/
Hope it helps.

A: In AWS S3, the number of requests, relates to the total number of HTTP requests sent to the bucket, such as PUT, GET, DELETE.
However if you use multi-part upload, each part goes as a PUT request and the total number of requests goes high. This creates a relationship between the file size and the number of requests for multi-part upload.
Check the following Data Request calculation example:

Request Example: Assume you transfer 10,000 files into Amazon S3 and
  transfer 20,000 files out of Amazon S3 each day during the month of
  March. Then, you delete 5,000 files on March 31st. Total PUT requests
  = 10,000 requests x 31 days = 310,000 requests Total GET requests = 20,000 requests x 31 days = 620,000 requests Total DELETE requests =
  5,000×1 day = 5,000 requests

Reference: S3 FAQ
