Most games that have some sort of betas and alphas make them free, but the full version (when it eventually comes out) is payed most of the time.  If the games full version is paid than the game will lose most of  its attraction, (wich happens often) but you'll get money from the people who have the cash and that loved the betas and aphas. Those people are usually whales (aka big spenders) of some sorts, but if the games full version is free it'll not get much money from the start vs the paid version, but it'll last longer wich usually makes it so the free version makes more money than the paid version through patreon, special items that you get buy paying usually as  costumes or dlcs.  Usually paid games also have costumes and dlcs but they dont premote as much as free version wich makes  it les money than free version

Free version

+Longer attraction than paid;

-Wont get as much money from the start as paid;

+After couple of moths/years/weeks will make more money than paid;

+Can add  the option to pay for the game at the end or when you open the game; 

-Most likely seen by whales not as guality experience as a paid game.

Paid version

-Lower attraction than free;

+Will get a lot of money from the start unlike free version;

- It wont make as much money as free over a couple of week/month/years;

- Wont have to pay for the full version because its basically paying 2x for 1 game;

+ Most likely see by whale as higher quality than a free game.

Both versions

add extra ways of paying for the game patreon/dlcs/costumes.

This is only my opinion this is there game and they can do anything they want to do with it.