From “Transformers: Dark of the Moon” to this past weekend’s “Conan the Barbarian” and “Fright Night,” Hollywood has spent the summer debating the aesthetic gains of 3D. But in the more crucial barometer — how much of a boost 3D upcharges bring to the bottom lines of studios and exhibs — the summer has provided mixed messages.

In 2010, 3D’s contribution to a pic’s overall B.O. ranged from about 50% to as high as 80%. This year, the domestic figure is down to roughly 45%. But pics are still seeing more formidable 3D returns overseas, with the format accounting for about 60%-70% of a film’s international take, even in territories where the upcharge is a bigger percentage of ticket prices than domestically.

To some degree, the divergence can be chalked up to a matter of preference — some cultures just like 3D more than others for reasons that can’t be quantified, and big-budget f/x spectacles continue to draw big auds overseas — but there are also some subtle differences in local pricing models that provide insight to studios and exhibitors eager to see 3D pay off on its promise of enhanced B.O. takings.

Some notable factors: Many international markets temper 3D upcharges with discount play periods. China has half-price Tuesdays. In Germany, “Cinema Day” brings a steep midweek price drop to matinees. And some territories even charge less for 3D pics that have shorter running times. In many countries, premium ticket prices for 3D are further mitigated because moviegoers are encouraged to buy their own reusable glasses.

Domestically, studios have had to lower their expectations as to how much 3D can boost grosses. This summer, for instance, “Pirates of the Caribbean: On Stranger Tides” saw 3D account for 46% of its U.S. grosses. “Harry Potter and the Deathly Hallows: Part 2” — the first installment in the franchise to be released in 3D — tallied 43% of its grosses in 3D.

In Mexico, a higher-than-average 3D upcharge and high rate of family filmgoing have eroded the format’s performance.

Pics in 3D cost Mexican auds on average an extra $2.40 vs. 2D tickets, which cost around $3.52, according to an IHS Screen Digest report. The country’s largest circuits, Cinepolis, Cinemex and Cinemark, charge between $2.20 and $2.77 more for 3D than 2D. Though Mexico has the lowest average ticket price for 3D films, recent 3D titles like “On Stranger Tides” and “Transformers” tallied some of their lowest 3D shares (42% and 55%, respectively) in the territory.

But elsewhere abroad, the percentage of upcharge seems to have little effect on the format’s popularity.

In mainland China, 3D tickets cost between $12 and $18 compared to the country’s average 2D ticket price of $9.39. But Chinese moviegoers rarely pay full fare: Besides half-price Tuesdays, online group purchases can cut 3D ticket prices in half, and some theaters discount purchases by certain credit-card holders.

An aggressive 3D rollout has made China one of the biggest boosters of the format, as 3D accounted for the majority of B.O. for “Transformers,” “On Stranger Tides” and “Harry Potter,” with 82%, 64% and 70%, respectively, in the market.

Established territories Japan and Germany continue to post topnotch results for 3D, and developing markets such as Brazil and Russia also turn out well for the format. Moviegoers in Brazil boosted first-quarter 2011 3D totals 58% over the same period in 2010, helped primarily by local 3D expansion. (Each new Brazilian plex has at least one 3D screen.)

Going to a 3D show in the big theater is more of an event destination,” said Paramount Intl. prexy Andrew Cripps, referring to 3D turnout in territories such as Japan and Russia.

Indeed, total Japanese 3D box office in 2010 ranked second only to the U.S., with $471 million, according to the IHS report, while Russia rounded out the top five with $336.5 million from the format. This year’s highest-grossing titles, “Harry Potter” and “Transformers,” delivered some of their highest 3D results in Japan and Russia.

Despite a much higher 3D premium by percentage for Russian moviegoers vs. 2D prices (at around 36%, according to St. Petersburg-based firm NevaFilm), 3D still rakes in considerable coin there. Japanese filmgoers pay an average 3D upcharge of $3.79, or 27% over the $15.68 average ticket price. And it can be much higher in some locales: In Tokyo’s downtown Roppongi Hill theater, for instance, 3D tickets cost as much as $5.11 more than 2D.

Some Japanese exhibs ease 3D ticket prices by charging less to those who bring their own glasses. Dolby controls most of the Japanese 3D market, and in March, the company started offering reusable 3D glasses for $12 per pair. In Europe, RealD sells its reusable glasses at concession stands or the ticket window for about E1, saving auds the repeated expense.

Every country is in different stages with the glasses,” said Par’s Cripps. “(But) in most countries, the glasses are bought by the consumers.”

Elsewhere in Europe, both Germany and France generally charge more for 3D pics than in the States — but are turning in higher 3D shares.

In Germany, the average uptick for 3D vs. 2D runs around 43% ($3.85 more in 3D); French auds pay $3.10 more per 3D ticket for a 35% difference. At the high end in Gaul, 3D can run up to $30 per ticket (as it did for the “Harry Potter” premiere at Paris’ Bercy stadium), while at Cinemaxx in Berlin, “Potter” in 3D cost almost $20. Neither extreme hurt the film’s opening weekend: “Potter” debuted with 70% from 3D in Germany and 65% in France, which currently boasts Europe’s highest 3D screen count at 1,606.

What’s more, German auds sometimes have the option to pay less for shorter, lower-profile 3D films. For example, at Cinemaxx on the opening Saturday, “Potter” tickets cost $19.40 in 3D, while “Green Lantern,” with a 15-minute shorter run time, cost $17.95 during its comparable showing.

According to Cripps, different pricing on 3D films with run times shorter than 2 1/2 hours may be a way to alleviate resistance to higher prices for family pics.

In general, event movies are going to hold up better than family films,” Cripps said, adding that most toons have incredibly long legs — but not necessarily for their 3D runs.

3D isn’t working everywhere overseas, however.

Spain is seeing the format’s biggest downslide (at least in Europe), crippled by a 22% unemployment rate and rampant piracy. The country’s 3D premium at 37%, or $3.05 more than 2D, also is contributing to the format’s decline. “Transformers” grossed 49% locally from 3D, while “Pirates of the Caribbean” earned 41% and “The Smurfs” earned 39%.

(Clifford Coonan, James Young, Mark Schilling, Ed Meza, Nick Holdsworth, Marcelo Cajueiro and Elsa Keslassy contributed to this report.)