Hi @Rabih Naouss,
Sharepoint 2019 supported operating systems are Windows Server 2019, Windows Server 2016, Windows Server 2022. You will need to upgrate Windows Server 2012 R2 to 2016 to install the SharePoint 2019. Please refer to following document
Upgrade an existing AD FS farm by using Windows Internal Database
Software requirements for Project Server 2019
For the licenses of 2019, you could use free trial after download the SharePoint 2019. It provide a trial key under install introductions
https://www.microsoft.com/en-us/download/details.aspx?id=57462
Regarding the selling price of the license, the real-time price may be different. I would suggest you consult the local sales team for more accurate information.
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