How can I find the size of all tables in AWS DynamoDB?

I have about 50 tables in DynamoDB and I'm looking for a way to find size of all tables.

aws dynamodb describe-table --table-name [table name]

I know above command returns TableSizeBytes, but is this the only way to get size of table? Do I have to run this command for all tables in picture? Also, what is the cost of running this command?

Just write a script and loop over all your tables. As already stated there's no cost for running the command.

For example:

#!/usr/bin/env bash

YOUR_DYNAMODB_TABLES=( "table1" "table2" "table3" )
TOTAL_SIZE=0
for TABLE in "${YOUR_DYNAMODB_TABLES[@]}"
do
    SIZE=$(aws dynamodb describe-table --table-name "$TABLE" | jq '.Table.TableSizeBytes')
    TOTAL_SIZE=$((TOTAL_SIZE + SIZE))
done
echo $TOTAL_SIZE