No wonder people cry at weddings, with costs like these

Weddings aren't cheap — even if you're not the one getting married. 

The average guest spent $703 for each wedding last year, with millennials (who are arguably more apt to be in that everyone-I-know-is-getting-married phase of life) shelling out even more, at an average $893 per celebration, according to the American Express Spending & Saving Tracker. Multiply that by an average three weddings per year, and celebrating other people's marriages is no small expense.

A big contributor: One in five weddings is a "destination wedding" somewhere other than the couple's home, per The Knot. Those travel costs can add up for friends and family attending. 

Nearly 40 percent of consumers say they have spent more than $600 on travel for a wedding, according to a new survey from Priceline.com. That includes 15 percent who have shelled out $1,000-plus. The travel site surveyed 1,016 adults age 21 and older during February.

Try these five strategies to keep costs in check:

Before you RSVP "yes," gauge how much you'll have to spend to attend. 

Four in 10 invitees told Priceline they have RSVP'd "no" to a wedding due to high travel costs. Scour the invite and wedding website, too: Certain wedding details, like a black-tie dress code or no kids allowed, can be red flags for extra expenses.

Weigh that wedding against others on the calendar and your overall budget, said Sophia Bera, a certified financial planner and the founder of Gen Y Planning in Austin, Texas. You may need to prioritize: Passing on the bachelor party in Las Vegas to afford attending that friend's wedding, for example, or skipping a college classmate's nuptials so you can see your sister get married.

"You don't have to go to every wedding you're invited to," she said. "Financially, you might not be able to."

Check travel prices before you commit to attending the wedding. Aim to book shortly after you send in that RSVP and are certain of your plans, said Adam Goldstein, co-founder and chief executive of travel search site Hipmunk.

"You don't want to wait too long, because the things you're looking for might sell out, or go up in price," he said. 

Cast a wide net for deals. Wedding room blocks can be a good value, but the hotel might have other promotions that are even better, Goldstein said. Check other local hotels and vacation rentals, too. 

"One of the most obvious things is, make sure you're looking at all the area airports," he said. "Sometimes it doesn't make any difference; sometimes it can save hundreds of dollars."

Come up with a budget and a savings plan as engagement announcements stack up, said Bera — especially if you can foresee a few celebrations that you'll have a tough time saying "no" to. Setting aside a little money each month can lessen the blow when you need to make travel arrangements or buy that gift.

If you're using a rewards credit card, think about saving and redeeming your points or miles strategically, she said. New cardholder bonuses can often be enough to cover a round-trip flight (or two), and many offer bonuses for redeeming on travel. 

Steer clear of this strategy if you're carrying credit card debt. 

"Unless you're paying off your credit card in full every month, I don't recommend opening up new cards," she said.

How much to spend on a wedding gift is a big stress point for guests, said Jen Glantz, founder of Bridesmaid for Hire. During 2016, the average cash gift was $160, according to wedding-registry site Tendr, with some variation in wedding gift trends by region and season. 

But don't base your gift on benchmarks like that, or what others are giving or the couple's cost per guest, said Glantz. 

"When you give a gift, it should be how much you can afford to give," she said. 

Check out the couple's registry early, when you're more likely to see options in a wide range of price points, said Glantz, who is also the author of "Always a Bridesmaid (for Hire)." Then stack coupon codes, sales and credit card rewards to trim costs. 

Join forces with other guests, Goldstein said. It's a fast way to knock down travel costs like a car rental, hotel room or vacation rental. 

Going in on a group gift can be another way to make the most of your budget, especially if the registry has already been picked over and only big-ticket items remain, said Glantz.