Parents are being warned to beware of so-called free games that can turn out to be very expensive indeed.
From Candy Crush to Final Fantasy, so-called 'freemium' games are some of the most popular on the web, with more than a third of people saying that they play more than five times a week.
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These mobile apps or online games are initially free, but offer players the opportunity to purchases extras, such as lives or special items, through in-app micro-purchases.
It's easy enough for adults to get hooked on games, and 17% of people say they're addicted to at least one, a survey from GoCompare has revealed.
Some of these games are generating an astonishing £1 million a day from in-app purchases - and, all in all, we're spending a whopping £90 million a year.
"Free-to-play mobile and social media games can be a great way to kill some time, but the often simple yet frustrating format can encourage a 'just one more go' mentality," says Matt Sanders of GoCompare Money.
"In-app purchases are usually fairly cheap, but spending £2.99 here and there for extra lives or an item to help you beat that one level that you've been stuck on all week can quickly add up."
In one shocking case in the US, for example, a man spent an eye-watering $1 million playing Game of War.
Even more worryingly, one in ten people say their children play these games regularly - and 8% say they've run up a bill. In some cases, people have been billed thousands of pounds.
"While giving your child a smart phone or tablet to play with may seem innocent enough, but if your card details have been stored on the device, they could quickly rack up a hefty bill by the push of a button," says Sanders.
Parents are recommended to visit the app store and set up a password that has to be used to authorise any spending - before letting their children loose.
So where do people spend the most? Average spend on in-app purchases by region:
1. East Anglia: £24.73
2. Northern Ireland: £21.79
3. West Midlands: £21.73
4. Yorkshire and the Humber: £18.58
5. North West: £14.61
6. London: £13.76
7. East Midlands: £12.25
8. Scotland: £9.41
9. Wales: £9.36
10. North East: £7.07
11. South East: £6.91
12. South West: £5.61