No, that is not accurate. You seem to be slightly confused about SalesforceDX, and its interactions with VSCode (via the official plugins).
SalesforceDX is not a paid add-on like, say, a full-copy sandbox (or an additional one if you already have it). As long as you have a paid org, you have access to all of the features of SFDX.
What the VSCode plugins require are the Salesforce CLI to be installed on your local machine. The Salesforce CLI is free to download, install, and (partially) use for everyone (even developer edition orgs) as far as I know.
There are parts of the Salesforce CLI and the VSCode plugins that you won't be able to use without a dev hub org (dev hub can only be enabled in a dev hub trial org, or any paid org) like creating scratch orgs and pushing/pulling metadata to/from a scratch org, but the CLI and VSCode plugins can be used without that.
Probably the biggest drawback to using the CLI + VSCode plugins without having a dev hub org (and thus without the ability to create/manipulate scratch orgs) is that you lose the comparatively rich feedback that we had with the old force.com IDE or things like MavensMate.
Without scratch orgs, the flow is write code -> save -> CLI to convert to metadata form -> CLI to do a metadata deploy to your org of choice. The compilation error messages surfaced through that flow are not up to snuff in my opinion (at least at time of writing), and extra work is required to really get decent integration with VSCode.