I see no problem with the way they are charging. Most stuff can be gotten without paying a cent if you are patient, lucky, and have in game gold. Only things that can't are the extended day storage from the starter kits and some of the recipes and its possible that I just haven't been lucky enough to be offered those recipes by adventurers . I don't mind the wait for new days either but really think the cap should be upped. Up the cap to 30 and give the people who paid for the extra the amount extra they bought on top of the 30. Would make it so I don't waste stored days when I am asleep or at work.
Fun but a few flaws in it. First too often there are 1 damage attacks. Secondly its too short, really should have been double or triple the size. Also there should be more options to increase when you level up. Over all i liked it even though the gameplay is a little slow but with a few improvements it would be a much better game. Hopefully if you make a second of these you will fix some of the flaws.