"It's not a problem for companies which collect customer data for internal use only. It's a big problem for companies which sell that data."

It has nothing to do with companies selling data. It's a problem for any startup that uses US SaaS companies, e.g. AWeber. You can't do that anymore even with correct ToS, with double opt in, with their consent to send people emails.

Migrating to companies into the EU is no option, as there is none with the eco system and 2nd level SaaS like Mailchimp or AWeber.

And companies large US tech companies like Facebook are not impacted, as they will require consent to data transfer into the US during sign up.