是的，Amazon AWS会每月重置成本。可以使用AWS的Cost Explorer API来获取每月的成本信息。以下是一个Python示例代码：

import boto3
import datetime

# 配置AWS账号信息
session = boto3.Session(
    aws_access_key_id='YOUR_ACCESS_KEY_ID',
    aws_secret_access_key='YOUR_SECRET_ACCESS_KEY',
    region_name='YOUR_REGION_NAME'
)

# 获取Cost Explorer客户端
client = session.client('ce')

# 计算上个月的时间范围
now = datetime.datetime.utcnow()
end = datetime.datetime(year=now.year, month=now.month, day=1)
start = end - datetime.timedelta(days=30)

# 发送请求获取成本信息
response = client.get_cost_and_usage(
    TimePeriod={
        'Start': start.strftime('%Y-%m-%d'),
        'End': end.strftime('%Y-%m-%d')
    },
    Granularity='MONTHLY',
    Metrics=['UnblendedCost']
)

# 解析响应数据并输出
cost = response['ResultsByTime'][0]['Total']['UnblendedCost']['Amount']
print('上个月的成本为: $' + cost)