THERE’S a homily I’m fond of which underlies an ongoing conversation in gaming about post-purchase content sales.

The story goes that when placed in a boiling pot a frog will immediately jump out as the water is shockingly hot. But when placed in a pot which is slowly heated, the frog will boil alive, as it doesn’t perceive the increasing temperature.

The angry reaction of older gamers to the phenomenon of being sold games which have been cut into increasingly expensive chunks fits into this analogy — we feel we’re being boiled. But for people who only started gaming more recently, the reaction is more often, “hasn’t it always been like this?”

Only a few years ago, buying a game meant buying the whole game, everything included. Expansions were always there, but these tended to be planned after a title was clearly a success — as a sort of halfway house before a sequel.

Today, however, gamers are faced with a deliberately bewildering array of wallet-sucking extras, all hived off from the original product.

Paid-for downloadable content, season passes, individually sold maps, guns, skins and even difficulty levels have been cheerled by the likes of The Sims (buy a pool! Buy a chair!) to Team Fortress 2 (buy a gun! Buy a hat!) and Hearthstone (spend £50 trying for virtual cards we’ve arbitrarily decided will be rare!)

Morning Star sports editor Kadeem Simmonds, an avid console gamer, argues that his preferred platform has been hit hardest by this trend. Having bought a multiplayer game with five maps, just months later with the introduction of new ones he is left with a choice of either buying those as well, or effectively stopping playing as everyone else shifts over.

Sports games meanwhile are even worse, with almost everything up for sale and the possibility of paying hundreds of pounds to “get it all,” only to find that 12 months down the line it’s obsolete with the release of the next version, most notoriously in the case of EA’s franchises such as Madden NFL or NBA Live.

And this year EA had a nasty extra surprise. On top of Madden 2015’s £45 cover price, if you want to get the Ultimate Team Mode that’ll be another £45 please. In the terms of just a few years ago that’s a £90 game.

For companies which control titles with strong fan bases, this sort of behaviour is increasingly the standard, a fully exploited cash cow based on two of the oldest human attributes around — completionism and addiction.

First hook someone with a mechanic which offers rewards and praise in exchange for a commitment of time in a controlled environment — an achievable endorphin rush which is much more reliable than gambling.

Make progression along a path to what seems a realistic completion goal easy at first, then slower and slower to reach. Open a financial path to completion. Then once most of your punters have reached the first goal, offer an “expansion” (paid for, naturally) which extends completion slightly further out of reach.

And the kicker is that this expansion occasioning a secondary rinsing of customers can in many cases be done at almost no extra cost to the publisher.

Making a new asset for a game, a weapon for example, and adding some stats once you have the main engine in place is child’s play — in fact children do it all the time in moddable games such as Skyrim.

For an experienced 3D artist, modelling an item might take between a day or a week of work and before the item goes up at the Mann Co. store in Team Fortress 2 for £1.50. Publisher Valve can then sell this new toy 100,000 times over for little more than the price of a fast internet connection. It made $139 million (£90m) doing so in 2013.

This hugely profitable capitalist cynicism plays directly into elements of the human psyche which drive us to spend small sums over and over again to feed addictions, without necessarily realising that we’re running up huge bills.

A Reddit poll submitted in November 2014 for example was full of people talking about spending hundreds, in some cases thousands of pounds on digital TF2 items as though it’s normal behaviour where if someone asked them to just buy a full-featured game for that sort of money it would be laughable. But they, like the gambler or the boozer before them, have become as the anecdotal frog — boiled by slow degrees.

Complaints have been growing over this explosion of misdirection and consumer exploitation.

But games multinationals can weather online whinging as long as they are free of physical consequences. They need to be actively held to account for their behaviour, which locks people without cash out of large parts of the games they save up for while rifling the pockets of those who can afford it or worse, the pockets of those who can’t afford it but lack the will to say no.