[himmelreiter]

I'm participating since a few months in the closed beta of SHO.
The shop model uses prestige points (PP) and credits (CR) to sell items. At his time (May 2013), the PP are balanced properly against the resources you need during combat (mostly fuel and torpedoes). It is possible to advance in the campaigns without using any CR you also gain from accomplished missions.

But - and here comes the payment model - if you like to have better items (e.g. better torpedoes, a type VII-C/41 boat instead of the standard VII-C) you have to invest CR. Speeding up installation time of technology can also be done with CR. For a bulk purchase the CR acquired from completed missions are definitely not enough. You have to stock up CR with real money.

Conclusion: I suppose I will be able to play SHO a long time with only occasional real money investment and accept lower quality torpedoes, long build time for next generation boats, long transfer times for technology. This comes true because SHO is not my main game. It is more the community and strategy game to be played a few hours the week.
There will be people buying the best of all for many CR, thus investing a bunch of real money from time to time.

For serious subsim game play we have all the other simulations.