No actual game/app distribution will begin until the beta ends "later this year," at which point developers using the SDK will need to contract up, to the tune of $99 a year. The SDK is free until then.
Thanks to the beta's FAQ, we also now know that completely free/ad-supported apps will not be allowed on the service, and that "development will be limited to paid (including freemiun [sic]) content." In-game/in-app microtransaction functionality will be added to the SDK at a later date during the beta.
As far as PlayStation Suite's actual app pricing structure is concerned, both in terms of its consuming-facing strategy and its back-end developer percentages, Sony hasn't quite ironed that out: "We can't provide detailed information at this stage, but we are considering a pricing structure based on current market conditions."