This is a complicated discussion. It gets stranger still because when the dollars don't matter, people will say one thing and then do another.
I will share some of my own thoughts on this subject because I think it's important. Hopefully I don't offend anyone or touch off any alarms. Money is a touchy subject.
First, I'm not looking to make Minecraft-millions. Certainly that would be nice but I'd be much happier with a long term sustainable income that would let me work full time on the game. (That being said, when you factor in the stage of life I'm in [wife plus two kids] and risk factors, this amount might be more than you think.) I don't need to be flying a jet all over the country. I'm not that fond of traveling and really I'd rather be writing code.
Along those lines, I would nearly give the game away if I could find another way to earn revenue from the game. For example, if for some reason the modding community really takes off then I'd like to offer a sort of "app store" for modders to give away or sell their mods. If they are selling their mods then they can take advantage of whatever basic copy protection scheme gets built into Mythruna, they get to list in my store, and the store would take a small cut of that mods sales. And if you want to run your own server and charge your players, I will help facilitate that too, if you like... one time fees, subscriptions. or whatever. All hooked into the mythruna.com server listing service and player accounts. (I will also be willing to license the engine itself for "total conversion" style devs but I don't know if there would be interest anyway.)
If all of that brings in lots of revenue then it will lower the price of the game.
There has to always be some transaction cost in this case because what I'm really selling are "accounts". If accounts were free then everyone would have one (spammers and phishers included) and they become nearly worthless while still costing me money in database space, server usage, etc... small amounts but not zero. Given this and other factors... and the size of the ultimate game, I would probably never sell it for less than around $5. Perhaps with bundling options, etc. for add-ons as described above. Who knows. It's dependent on a thriving community anyway... and that community would probably like to know that the shoppers have at least a certain amount of buying power. $5 seems reasonable as a minimum.
However, it is also a likely scenario to consider that most mods might be given away by the players or the community never achieves critical mass or whatever. In that case, I need to focus on the raw game price.
I waffle on this one all the time. One day I will be in the same mindset you are and on another day I'll be thinking $15 flat rate indefinitely. The truth is that good business would be to charge whatever the market will bear. It's just hard to figure out what that is... especially since I'd be happy earning a comfortable living doing what I love to do.
At any rate, soon early adopters will get to pick their level of faith and interest monetarily. I will be setting up a store for people who want to buy in at different prices for whatever reason. Some players really want to support the game and feel like they are a special part of what makes it a success.
Some time in the next few weeks (I hope) I will open up the store for players who want to pay now (rather than wait until alpha when everyone has to pay). This is also sort of a grace period where you can get the full client license for a discount rate that will go up when the game hits alpha. Players who pay more than required will get special thank you gifts at different points in the game's release cycle.
(Note: the game continues to be free to play during the pre-alpha period. These are optional purchases.)
(Note also: the following are just examples and may move around a little, ie: are subject to change.)
An example set of options would be like:
Level 1) $5: gets you a player account on Mythruna.com (so you can login to any server with that account), access to a private players-only group on the forum, and $10 off the game when it hits alpha.
Level 2) $10: a player account, group access, and full client license when the game hits alpha (saves $5 if the alpha sells for $15)
Level 3) $15: all of the above plus some other little thing... stickers or something. Or a "registered server" account (more on that another time).
Level 4) $50: all of the above plus access to a private group for high-donators and your name in the game credits
Level 5) $100: above plus get to help name and contribute to the design of one of the NPCs that will appear in the town/city near spawn... and associated game credit. For example, you could have you or your character as permanent residents of everyone's game.
Level 6) $150: above plus a signed and numbered full-color hard-back version of the "Creatures and Races of Mythruna" book that I plan to produce. (This book will only sell in paperback form when released on Amazon.)
I may juggle those around a little and I have a few more ideas I'm still toying with. But for example, the level 3 option me be more appropriately at $20 or whatever. I'm also entirely open to adding additional levels in the gaps if some player wants to pay X but there is no option for that. And if for some strange reason a hundred people sign up to get to put an NPC in spawn town then I have to start cutting that off or making it more expensive. It's all fluid in that respect. I can't have 1000 custom NPCs running around spawn town.
So in the end, the early adopters and true believers will get to vote with their dollars on what they feel the game is worth... and get a little something extra for the trouble.
Thanks for reading this far. I hopefully I haven't stirred up trouble.