I would recommend talking to a Tableau sales rep. as they can "work the numbers", ask other questions e.g. what's your estimated growth rate?, and apply discounts.
Server licensing costs are transparent and Sales contacts will give you the definitive story. Everyone gets the same price from them so they will give you a realistic idea of overall cost.
Now of course you have Tableau Online to consider which uses a different cost model and is worth looking at.
I hope Tableau can make this change soon. I'd love to be able to share dashboards internally with all of our staff (2,000+) on our company's internal web-based systems but the Tableau Server licensing model just doesn't make this possible for us. Right now it's limiting the impact of the dashboards we create, and thereby the effectiveness of Tableau.
There's a bit of discussion on LinkedIn around the volume discounts you can extract. It's definitely not $1K a user once you get going.
I too would like to see a split in server licensing. Currently it's one cost for Interactor which gives interaction, editing and dataserver and whatever else comes along. I'd like to see a cheaper interaction only license because that's all the bulk of users will be using.
You need to have this conversation with your Tableau sales rep. Here's the quick answer: Tableau does not presently have a concurrent named user licensing model. For your use case you will need a core license or a named user license capacity of 300.