Ship of Heroes will require a subscription to play. Pricing has not been finalized at this time, but in response to a forum post on the official site, Casey McGeever aka "The Consultant" wrote that final pricing will be "in the ballpark" of the chart below:

Term Price
per month $15.00 US
3 months $40.00 US ($13.33/mo)
6 months $70.00 US ($11.67/mo)
12 months $120.00 US ($10.00/mo)

McGeever went on to clarify that final pricing will be determined closer to Game Launch

We're probably not going to actually settle most of the prices until we get closer to launch because it would be tragic if we underestimated some of our costs and committed too early to pricing that did not break even. But one thing we have said pretty clearly is that the model is to keep the costs reasonable and to recycle the cash that comes in over the bare operating costs into additional game development — more powers, more archetypes, more missions, more worlds, more craftable stuff…