Hawaii helicopter tours cost several hundred dollars per person. On two islands they show you land that no road reaches; elsewhere they show you what you could have driven to.
Kauai: the strongest case
Roughly two thirds of Kauai has no road access at all.
The Nā Pali coast interior, the amphitheatre valleys, Mount Waiʻaleʻale's crater — one of the wettest places on earth, with waterfalls streaming down a thousand-metre wall — and the Wailua falls system are aerial-only or multi-day-hike-only.
This is the flight that genuinely shows you something otherwise unavailable.
The alternatives: a Nā Pali catamaran gives the coast from sea level, which is different rather than equivalent. Waimea Canyon's road viewpoints are free and show the island's interior scale.
The Big Island: depends on the volcano
Operators fly over Kīlauea's caldera and lava fields, which is worthwhile geologically — the scale of the flows and the fissure lines is not legible from the ground.
Glowing lava requires an active eruption, which is unpredictable and cannot be booked. Any operator implying otherwise is overselling.
Check the USGS volcano status before deciding.
The other Big Island flight covers the Hāmākua coast waterfalls and valleys on the wet windward side, which is reliable regardless of the volcano.
Maui and Oahu: weaker
Maui flights cover Haleakalā's crater and the west Maui mountains. Both are impressive and both are substantially accessible by road and on foot — Haleakalā has a summit road and hiking trails into the crater.
Oahu flights are largely a coastal circuit of an island with a good road network.
Neither is bad. Neither is showing you unreachable land.
Doors-off, and other choices
Doors-off flights remove the doors for unobstructed photography, with a harness. Colder, much windier, loose items prohibited, and usually more expensive.
Some operators restrict it by weight distribution and weather, so it cannot always be guaranteed at booking.
Fixed-wing small plane tours cost less and cover more ground, without the ability to hover or fly as low.
Seating is often assigned by weight for balance, so a window seat cannot be guaranteed — worth knowing before paying for a photography flight.
Safety, said plainly
Hawaii's tour helicopter sector has had fatal accidents, and this has been the subject of regulatory attention.
What a passenger can reasonably do: choose operators with a long operating history, ask about their safety record and maintenance, and accept a weather cancellation rather than pressing for the flight.
An operator who cancels in marginal conditions is showing you something useful.
Practical
Book for early morning — air is calmest and light is best, and afternoon cloud builds over the interiors.
Build in a spare day, since weather cancellations are common.
Wear dark clothing to reduce reflection in the window if photographing.
Cost runs roughly $250–450 per person for a standard hour, more for doors-off and longer routes.