"prime benefit" is correct and usable in written English.
You can use it when referring to an advantage or benefit that is the best or most important of a particular group of advantages or benefits. For example, "The prime benefit of investing in a retirement plan is the tax savings."
For MTV, a prime benefit of "The Real World" is its relatively low cost, about $300,000 an episode.
A prime benefit to rural communities is the close-knit sense of mutual support that led to the creation of Alianza de Mujeres Activas (Alliance of Active Women).
Despite the lack of research, many experts share the view that people who take their work to their workout are missing a prime benefit of exercise: its ability to reduce stress.
The prime benefit to each of these politically connected people was money -- in the form of what are known as marketing, agency or "finder's" fees -- that the investment firms paid them for providing entry to Mr. Silvester's office.
They say that the prime benefit of a tablet computer the ability to enter notes and manipulate software programs with a "pen" (actually, a plastic pointer)—makes these devices vastly more useful than the two things they're most likely to replace: traditional notebook computers and clipboards, especially around the office.Tablet computers come in two varieties.
It was precisely the normalcy of the exquisite that was the site's prime benefit: crystal and leaded glass, polished wood and thick marble and expanses vast enough to conjure an air of vaguely naughty mystery were, it seemed, what life was supposed to be — perhaps not in substance but in essence.
The program is half the price ($49/year), while still offering free two-day shipping and other Prime benefits like Prime Instant Video, Prime Music, access to the Kindle Lending Library, along with other promotions aimed at students.
Amazon cut back on Prime benefits, making it so that Prime users can now only share Prime benefits with one other adult.
They cite surveys showing that The Sciences has consistently been rated as one of the prime benefits of academy membership.
Customers who become full Prime members can cancel their membership at any time and we will refund the full membership if the customer has not made any eligible purchases or used any Prime benefits".
I don't take taxis all that often (I'm a big fan of my unlimited monthly MetroCard), but when I do, the conversations with the drivers are often one of the prime benefits, and I've often expressed to them my surprise that they haven't organized, or even unionized.
