I dont know this work, but have had a hand in some solar cell research (nanomaterials development), so can give a little context. This is a "one off" in so much as it will be centimeters sized lab based sample, although it has been repearedto verify. The current cost difference is astronomical versus mainstream (silicon) panels, but that's typical of new discoveries. To be more exact, this is TRL 4 (technology readiness level 4) which is a scale that goes up to 9. Things only start getting cheap as you get towards the top. As for what the expected price of these materials would be, we don't usually know for sure, although as this is a tandem cell it must be more expensive than mainstream as it literally builds a perovskite cell on top of a silicon one. They will never be used for mainstream - this is a specialist material.
The perovskite itself might make it as a general use solar cell. They have good efficiencies and you don't have to make pure silicon (which is a bitch) and can in theory make them cheap and easy. As for time frame, I'm a bit of a skeptic it will ever be really used as there are a couple of issues this tech needs to address before it's viable (#1, they degrade in air and encapsulating them adds new issues) and we already build silicon factories so that is soooo cheap versus building new factories to make long-term-cheaper cells. Factories are expensive. But in theory, anyone could push it to the mainstream within a decade.
Orville (with S4 pseudo confirmed!)