Somebody in the group always has the good phone plan. By the second morning they are the group's internet, walking around a foreign city with their hotspot on and their battery at 30%.
This arrangement survives until the group splits up, which every group does by the afternoon of day two. Two people go to the market, three go back to nap, one goes to find the thing they read about. The moment they are more than thirty metres apart, four of them are offline in a city they cannot navigate, and the meeting point they agreed on was "the square, around six".
The failure is not really about data. It is that the group made one person load bearing without telling them.
The three ways groups pay for this
Roaming is the default and the expensive one outside your own region. Someone always forgets to check, uses maps for a week and comes home to a bill with a number in it that ends the conversation about who owes whom. Inside the EU the "roam like at home" rules mean your own allowance travels with you, so a Spaniard in Italy has very little to worry about, beyond the fair use cap that some plans apply to data abroad. Fly to Morocco or Japan and the same phone behaves completely differently.
Airport SIM cards work and cost an hour. You queue, you hand over a passport, you do it again for each person who wants one, and one phone in the group turns out to be carrier locked.
An eSIM is the version that fits a group, because everyone installs their own before leaving home and lands connected. No queue, no shared battery, no single person responsible for whether the group can find each other. A week of data for a city break is usually a few euros a head, which is less than one round of coffees and considerably less than one roaming bill.
The partner we point people at is Airalo. You pick the country and install the eSIM before the flight. Two things to check first: the phone has to support eSIM and be carrier unlocked, and some plans want you to switch data over by hand once you land. Everyone buys their own, so there is nothing to split.
That link is an affiliate link. The price is the same as going direct and Billy earns a commission, which is what keeps the app free.
If one person does buy for everyone
Sometimes it is easier for the organised one to buy six of something and hand them out. That is fine, as long as it goes into the ledger the same day at the price actually paid. Small shared purchases are the ones groups forget, and they add up to more than anyone expects: the data, the first taxi, the coffee for whoever was late, the deposit on the boat. Individually none of them feel worth logging. Together they are the reason the final settlement never matches what people remember.
A rule that works: if you paid for someone else, log it before you put your phone back in your pocket.