Don't even start...

moving_slowly.py

import boto3

sess = boto3.session.Session(region_name='us-east-1')
s3res = sess.resource('s3')

gazillion_files = [('my-source-bucket', 'file-000000000001'), ...]

for f in gazillion_files:
    copy_source = {
      'Bucket': f[0],
      'Key': f[1]
    }
    s3res.meta.client.copy(
      CopySource=copy_source,
      Bucket='my-destination-bucket',
      Key=f[1],
      ExtraArgs={'StorageClass': 'GLACIER'}
    )
    ...