After recent updates added bulletproof vests and shotguns, it was probably inevitable that Prison Architect would continue it's escalation towards more and more exciting additions with each alpha. The trend continues in alpha 19 with a broad revision to the game's finance systems, which introduces new rules for borrowing, the need to pay corporation tax, and the ability to sell shares in your prison to investors.
Video update below while I try to explain why I'm not being sarcastic.
Alright, I'm being a bit sarcastic.
But Prison Architect's progression curve is linked to your ability to make money. If money is slow in trickling in - and it always was, unless you cheated or took loans - then your ability to build and expand your prison was slowed. When that's the core thing that's fun about the game, the obstacles that slow your progression need to be damned interesting to counter the frustration or boredom.
The largest change in alpha 19 is that it introduces the export room, which can be used to sell the goods your prison produces. You were already able to sell those items, but now you receive the money as soon as they're shipped off by delivery trucks rather than waiting for midnight. That should hopefully leave fewer hours of the day where you're broke and just waiting for pay day.
Beyond that, it's a set of very nerdy sounding updates that add, among other things, a bunch of new grant types and requirements, more uses for your accountant employee, and, yeah, the need to pay 30% corporation tax on all your profits. Unless you've unlocked an offshore tax haven.
See the full change list over at the Introversion blog.