I'll probably put the demo up on Steam once there's some proper story elements implemented. As for a full release with around 5-6 hours worth of content and supporting material, what would you consider a fair price?
If I may...I have purchased 100+ Indie games of various genre over the years, most of them not on sale, so i have a pretty good feeling for it.
If the current level of quality is maintained, the content in the previews is implemented and the genre standard ~15 missions are included in the release, I would expect it to release with a 25 to 30€ price tag (Microprose in particular has established this sort of pricing lately), but would personally feel 20€ to be the fairest price.
Under 20 I feel you may not make enough, given the likely niche audience. Over 30, people will be very hesitant to purchase it on release so the on-release sales, that make up the majority of many games' sales, may be dampened.
For particular regional pricings outside the EU/UK/US it gets kind of complicated, Steam sales assists Indie devs with that often.