RPG Insanity

The game is very unclear regarding how much I will have to pay, and how much content is paid only, or whether it can be grinded for like in Exe Create games.

Can someone clear it up for me?

The only things you might want to buy is the optional areas.

I think most Stat boosting items can be found in these areas.

(these areas aren't easy early though.)

How much does it cost, and can you buy it with ingame currency?

I don't know how much it costs because all items require in-game currency which I bought a lot but it wasn't good because I got bored of the game.. And the cost might change depending on country. So I don't know. But you can check it before buying.

And the game gives no way to earn in-game premium currency. 

I played the whole game without ever spending a cent. The bonus areas looked interesting but by the time I finished the game, I'd had enough of the dungeons (later on they get to be a bit of a pain; not too bad, but just a bit...)

IMO the game is definitely worth playing; I found it to be the only Kemco game so far that I could take a more "casual" approach - play for an hour or two, put it down for a few days, come back to it... the only trick is you've got to keep track of where you're supposed to go next (so maybe take just a few notes?)

It's an old game, cheesy graphics, cheesy dialogue, a couple of side quests that you have to really go hunting for - but all in all it was an enjoyable experience.