Well, with all due respect and from my point of view, if your game has an RPG mechanic of getting some items by purchasing them with a medium of exchange (which in this case are coins and valuable objects around the levels), when you would want to develop that mechanic due to the fact that, at this moment, the items can be found easily in the stages and then you would want to put in the stores more complex items that have an specific function (for example, access to an specific point of the world of your game), the complexity of the purchasing mechanic wouldn't be compatible with the easy ways to farm the way to obtain them (this could be an awkard example but I find it funny, this is the option to steal valuable items from one store in Link's awakening like the 980 rupees bow).

Regardless of the previous commented, since I have begun to play the game (since the 5.5 version in Y8.com if I am not wrong) and saw some of your videos in youtube (such as the plasticine to make the trailer, as well as you programming some of the enemies  like the sleeping green spiked balls) I can see that you manage to introduce your unique style combining references and mechanics of old platforming games (or from specific subgenres of the genre like Metroidvania, which I most like, something that you can see in my profile XD). That is more than enough for me to say that you are doing an splendid work and I will try to support your work when I have the chance to do it (I can even say that you inspired me to develop a new game in the future that I will try to make using LUA language in the Vbam emulator).

Awaiting your comments, Metroidvania researcher