Best Practices

I am attempting to arrange a tenant-to-tenant migration for 18 email accounts. I've reached out to 2 different companies, expecting 2 quotes at approximately the same cost. However, one quote is 8 times higher than the other, leaving me confused.

Could anyone provide insight into the typical price range for migrating 18 email addresses? Additionally, there are approximately 10 GB of data across Word, Excel, SharePoint, etc.

We intend to transfer 18 email addresses while retaining the domain name within an existing Microsoft 365 account. Our current account is hosted with GoDaddy Office 365.