It's important to think about the psychology of the situation… if someone's just had to forego the family holiday, then they're more likely to splash out on something much smaller to give themselves a bit of a boost. It doesn't negate the big sacrifice, or mean they're stupid necessarily. Willpower is also a limited resource, and the more you're having to hold back and hold back, the more likely you'll occasionally give in on something smaller.
George Orwell is interesting on this type of tendency:
Trade since the war has had to adjust itself to meet the demands of underpaid, underfed people, with the result that a luxury is nowadays almost always cheaper than a necessity. One pair of plain solid shoes costs as much as two ultra-smart pairs. For the price of one square meal you can get two pounds of cheap sweets. You can't get much meat for threepence, but you can get a lot of fish-and-chips. Milk costs threepence a pint and even 'mild' beer costs fourpence, but aspirins are seven a penny and you can wring forty cups of tea out of a quarter-pound packet. And above all there is gambling, the cheapest of all luxuries. Even people on the verge of starvation can buy a few days' hope ('Something to live for', as they call it) by having a penny on a sweepstake. Organized gambling has now risen almost to the status of a major industry. Consider, for instance, a phenomenon like the Football Pools, with a turnover of about six million pounds a year, almost all of it from the pockets of working-class people. I happened to be in Yorkshire when Hitler re-occupied the Rhineland. Hitler, Locarno, Fascism, and the threat of war aroused hardly a flicker of iinterest locally, but the decision of the Football Association to stop publishing their fixtures in advance (this was an attempt to quell the Football Pools) flung all Yorkshire into a storm of fury. And then there is the queer spectacle of modern electrical science showering miracles upon people with empty bellies. You may shiver all night for lack of bedclothes, but in the morning you can go to the public library and read the news that has been telegraphed for your benefit from San Francisco and Singapore. Twenty million people are underfed but literally everyone in England has access to a radio. What we have lost in food we have gained in electricity. Whole sections of the working class who have been plundered of all they really need are being compensated, in part, by cheap luxuries which mitigate the surface of life.
(Road to Wigan Pier, Ch 5)
The ordinary human being would sooner starve than live on brown bread and raw carrots. And the peculiar evil is this, that the less money you have, the less inclined you feel to spend it on wholesome food. A millionaire may enjoy breakfasting off orange juice and Ryvita biscuits; an unemployed man doesn't. Here the tendency of which I spoke at the end of the last chapter comes into play. When you are unemployed, which is to say when you are underfed, harassed, bored, and miserable, you don't want to eat dull wholesome food. You want something a little bit 'tasty'. There is always some cheaply pleasant thing to tempt you. Let's have three pennorth of chips! Run out and buy us a twopenny ice-cream! Put the kettle on and we'll all have a nice cup of tea! That is how your mind works when you are at the P.A.C. level. White bread-and-marg and sugared tea don't nourish you to any extent, but they are nicer (at least most people think so) than brown bread-and-dripping and cold water. Unemployment is an endless misery that has got to be constantly palliated, and especially with tea, the English-man's opium.
(RTWP, Ch 6)
The robovac is your friend's twopenny ice-cream, in effect.