You get EigenD and a year of free updates included in the purchase price of a Pico.
If you are not a recent owner and wish to update to the current version, the newest edition of EigenD currently costs £41 plus vat (£49 inc if you're in the EU) and you get six months of free updates with that version. You do not need to pay money to keep your Pico running if you do not want or need a new version of the software for any reason.
There is also a Pro version of the software now available. This costs more and includes the new Workbench tool for building and maintaining your own custom setups. You can easily upgrade to this from EigenD at any time.
You can see the various options here. When we originally launched Workbench we called the software sale a 'subscription' as it included a year of updates (and if you went for the top of the range Pro option with 12 months of updates it is over £200 hence that comment). This caused no end of confusion as it implied that you didn't own the software you bought and that you had to keep paying to keep your instrument going. This is not true (and was not at the time, the terminology seems to have confused people a lot and that is our mistake), you only need to spend money if you want to update the version, and those updates are free in your first year of instrument ownership anyway.
There is also a current free version of EigenD, 1.4 (which is the current shipping Stable EigenD in fact) and the main system is released under the GPL open source licence, so you can build your own EigenD at any time for no cost, if you're feeling particularly adventurous.
John