But there are a number of ways you can avoid them, or minimise them.
Use the Wifi
Most booking sites will now give you the option to select ‘free Wifi' as a must-have for your hotel.
However, it might be painfully slow, or it might be restricted to the common areas, with a heavy tariff for the high-speed service in your room.
If in doubt, check. But if it's an option, it's going to be the cheapest. Don't forget though, whatever you do, make sure you've turned ‘data roaming' off in your settings because most apps use data even when they're in your pocket.
DETAILS: Contact the hotel
Three Feel At Home
Three's deals with 42 countries give the widest free-roaming support of any of the main networks.
With the US, Australia and Sri Lanka on the list, on top of the whole of the EU and some other random ones, it's a no-brainer: just take your phone and use it as normal. You'll often only get 3G data instead of 4G, but it's better than nowt or being mercilessly rinsed.
If you're not a Three customer, check out its range of pre-paid SIMs that might be worth investing in if you're a frequent traveller, especially as most deals include some level of tethering.
COST: Varies (but free to most existing customers)
Local SIM Card
Buying a local SIM card at the other end is a good chance to test your language skills, but it's also the guaranteed cheapest way to get mobile while you're away. Of course that does mean you'll have a different phone number, but it's a small price to pay in every sense.
Do watch out as, in some countries, you'll have to sign-up to a contract with no minimum term, but you will need to cancel it when you leave or you'll keep getting charged by the month.
Be wary of special offer packs for tourists - they're usually more expensive than the locals get. Check your guidebook (Lonely Planet and Rough Guide usually cover this subject). Don't be tempted to buy a local SIM at this end. You'll almost certainly pay more that way too.
DETAILS: Your Guide Book
If all you want is that lifeline of Whatsapp and text, then your best bet could be ChatSIM, a global card with a modest price tag.
For less than the price of two beers in Stockholm, you can use WhatsApp, Telegram, WeChat BBM, Facebook Messenger and good ol' SMS - including emojis, for absolutely zilch extra. Nadda. Zip.
If you want to add photos, videos or calling, then you buy credits, For example, 2000 credits (£12) in most countries buys you 200 photos or 40 videos or 80 voice minutes. There's no option for full surfing though, so it's best used in a secondary device, but a more or less essential travel companion.
If you're a regular traveller, then you might want a device you can count on working first time, every time - especially if the company is paying.
In which case, this offering from French telecoms company Transatel could be what just what you're looking for. Available as just a SIM card, or with a 3G or 4G mifi dongle provided, the device comes with 25 euros of credit, which is worth 1GB in Europe.
The SIM is truly global, but the price changes. For example, in the Americas (including the US) it's a much steeper 49 euros for 500GB, so do check first. Transatel claims it's up to 90 per cent cheaper than roaming.
COST: 29 euros for the SIM, or up to 129 euros with a Huawei 4G hotspot (which includes 25 euros credit)
Y-ROAM dispenses with SIM cards altogether, instead opting for a rather chunky, Android-powered virtual SIM card affair, something we don't see often in the UK.
With partner networks in more than 100 countries, Y-Roam offers plans based on countries of usage, so a US pack is £15.99 per GB, or an EU one is a steeper (but still cheaper than roaming) £24.99. Further flung places command £34.99 per GB.
The box is £199, but that does include the first GB of worldwide data. The touchscreen device can accept two additional physical SIMs on top of the virtual one, and has a 6000mAh battery that can be used to charge your devices, thanks to a full-size USB port.