With all the complaints about escalating fees that travelers have to pay, another pricing trend is on the rise that some customers might actually like: paid upgrades.

Hotels, airlines and car rental agencies are more aggressively promoting the chance to upgrade your room, seat or set of wheels for a price that is often (but not always) less than you would have paid if you had reserved that business-class ticket or hotel suite in the first place.

Usually, these offers are presented at check-in, when travel companies figure it’s too late to sell their premium inventory to somebody else. But sometimes the upselling begins just after you’ve booked.

Elite members of travel loyalty programs are not necessarily happy about this development, because it can mean fewer free upgrades for them, although some companies are figuring out ways to keep these perks in the mix for their most loyal customers. Below are more details about who is offering paid upgrades and how to decide if they are worth the price.

A BIGGER ROOM

I stumbled onto a hotel upgrade last year in Hong Kong, after finding out the $250-a-night room with a harbor view that I had reserved was opposite the elevator bay. A trip back to the front desk to request a quieter room led to an offer to upgrade to a suite for an extra $12 a night. It was definitely a good deal (normally a suite would have cost at least $30 extra), and it made me wonder if I had been missing out by not bargaining more often at the front desk.

It turns out most travelers don’t ask for upgrades, and many clerks don’t offer them, so a company called Nor1 (nor1.com) has automated the process, essentially letting computers handle the negotiation. Working with chains like Hilton, Hyatt, InterContinental, Carlson and Fairmont, as well as independent hotels, Nor1 emails an “eStandby Upgrade” offer to some guests who already have reservations. The deals vary based on how full the hotel is, the type of room booked and variables like loyalty membership, but a typical upgrade invitation might offer a bigger room for an extra $10 to $30 a night.

Jason Bryant, Nor1’s founder, said the standby upgrade generally costs 25 to 40 percent less than booking the better room in the first place, since accepting the offer doesn’t guarantee you’ll get the upgrade (hence the word “standby” in the name). But if the hotel doesn’t sell that nicer room to someone else for the regular price, your upgrade will be confirmed when you check in.

Not everyone who books a room will automatically get an upgrade pitch, Bryant said.

“We don’t want 20 guests stacking up for the same offer if we know only one guest is going to get it.”

Elite members of a hotel’s loyalty program might still be offered a free upgrade, Bryant said, but could also see a paid upgrade option for an even better room or an offer of a discounted spa treatment or dinner instead of a room upgrade.

John Ollila, who tracks loyalty programs at LoyaltyLobby.com (and has elite status with the major hotel chains), said he usually tries his luck by asking for a better room when he checks in. But for travelers without elite benefits, he said, Nor1’s eStandby upgrades can be a reasonable deal.

“Check how much the upgraded room would have cost you in the first place,” Ollila said, adding that it might still be worth bargaining to see what you could get without charge.