Premium economy—upgraded coach service, typically featuring more legroom, priority airport services, and more amenities—is hot. And for good reason: At least in theory, it’s a win-win.

From the airlines’ perspective, it’s a high-profit product as well as a way of accommodating elite upgrades without displacing paid passengers in business or first class. For travelers, it’s a welcome escape from the crusher seats in regular economy, without the sky-high fares commanded by business or first class.

Alaska Airlines is the latest carrier to announce a new premium economy service, replacing its current premium economy class  offering, Preferred Seating, which is little more than a few bulkhead and exit-row seats with extra legroom.

The replacement, dubbed Premium Class, will begin rolling out in January on the airline’s B737-800s and B737-900s. The highlights:

• 4 extra inches of legroom
• Priority boarding
• Complimentary snacks and cocktails

Those four extra inches of legroom mean an increase in pitch from 31 inches to 35 inches. That’s hardly business-class legroom, but it’s a significant improvement over standard coach seating. Priority boarding is nice as well. But really, what you’re paying extra for is the added personal space.

The other key variable, of course, is pricing: How much extra will the additional legroom cost? Premium Service is only a win-win if it’s affordable, for paying passengers, and accessible, for elite members hoping for status upgrades.

As far as pricing goes, Alaska promises that Premium Service upgrades may be purchased for as little as $15 each way, but adds the qualifier that that’s “introductory pricing.”

In test bookings on Alaska’s website, the upgrade prices varied not just by route, but by flight. For a late-January flight between Los Angeles and Seattle, for example, a $64 Main Cabin coach fare could be upgraded to Premium for $31.18. The return flight, on the other hand, priced at $59 for Main Cabin, could be upgraded for just $16.13. There are, at least for now, some good deals to be had on Premium Service upgrades, but the value proposition isn’t a uniform one.

As far as elite upgrades go, MVP Gold 75K members of Alaska’s Mileage Plan program will be eligible for Premium Class upgrades at the time of booking. MVP Gold members can upgrade immediately on higher-priced coach fares, and within 72 hours of departure for other fares. And MVP members will be upgraded immediately on Y, Z, S, and B fares, and within 48 hours of departure on cheaper fares. Those upgrade opportunities are in addition to potential first-class upgrades, so the net effect should be an increase in cleared upgrades.

As premium economy products go, Alaska’s new Premium Services is at the bare-bones end of the spectrum, just enough of an upgrade to qualify for the “premium” designation. On the other hand, it looks to be attractively priced, which could make it a great deal for those looking for an affordable comfort upgrade.

Reader Reality Check

How much would you pay for an extra four inches of legroom?

After 20 years working in the travel industry, and almost that long writing about it, Tim Winship knows a thing or two about travel. Follow him on Twitter @twinship.

This article first appeared on SmarterTravel.com, where Tim is Editor-at-Large.