I suspect people are trying to say morality is SUBJECTIVE rather than objective.
I'm not sure this issue is really about differing moralities. Lots of people clearly do lie about their children's ages, but I don't think they do it because they have thought about it and decided it is morally right to lie about it and would be immoral to pay the full price. The reason they do it is quite simply that they don't want to pay the price the business is charging. They know that they are lying - of course, saying your child is one age when they are another, or requesting a ticket for an age group that your child doesn't fit into is lying.
I suppose morality comes into whether you think it's okay to choose what to pay, rather than pay the price set by the business. Many could call this fraudulent activity. Others seem to see this instead as 'bargain hunting' (although I would say a bargain is a low price set by the seller, not a low a buyer fancies paying). I'm not sure anyone would really say that doing this is 'right' and how many would go as far as to say it is not 'wrong' but actually just something they and others do. Saying you do it, doesn't mean you are saying it's right. And some people are certainly more willing than others to do lots of things that they know are not right and to varying degrees people are willing to accept to others and themselves that they are not right. They say that the more wrong things you do, the more your moral compass is blunted, so judging what is right or not becomes more difficult and more and more behaviours which many might question, feel more and more acceptable.
As others say on this thread. No one is perfect. No one does everything right. I don't think anyone is suggesting they do. And for someone to say lying about a child's age is wrong and they wouldn't do it, isn't the same as them saying that all people who do do this are evil and that themesleves who don't do it are better people. Lots of people who engage in lying about their children's ages and who failing pay the price businesses charge for children if that age, decide that the posters who wouldn't lie are judgey or highly critical of them.....probably I think because they are sensitive to the comments, because of course they know in their hearts that lying and cheating people out of money isn't really right behaviour. And when people feel others have a genuine case, they often become very defensive about it and come up with all kinds of reasons to justify their behaviour, when really knowing there is something in the criticism.
So I don't lie about my children's ages. I would see paying the wrong price as a form of theft. I feel awkward if I'm out with others who do it and I think that if you're not willing to pay the prices charged, you just shouldn't go. There will be other things I probably do that aren't right behaviour which perhaps others might be shocked by. Some of what I do, others might not like or might think immoral or questionable.
This thread isn't categorising people into good people and bad people, based on one action. In the end, we all do bad things at different times. However, that's not to say, that these individual things don't matter, or just becaue other people do different bad things, it's okay to lie and cheat businesses. Knowing others do different bad things can sometimes make people feel they have permission or the right to choose their own bad things and everyone can have some.
With all this stuff, in the end, I think a better approach to life isn't 'how far can I push it and what can I get away with and how far can I bend the morality or the law or whatever and just about feel okay about myself' but why not the opposite, and how little can I try to do this.
I am surprised at how people's consciences work sometimes and particularly how people justify their actions to themselves or on MN - they rarely want to just say 'i do wrong, I know it and own it' - this applies to people who steal from shops because their income is low and they have decided that they or their kids are as entitled to all the stuff richer people have, and that money shouldn't be a barrier to having stuff or experiences (one if the arguments used on this thread). Others are happy to cheat on their spouse or partner and come up with all kinds of justifications, while many would think cheating is wrong. Others steal or tell their children to steal school uniform from others, or trainers, or bikes, or coats. Others will hide a child in the boot of their car to avoid paying for them to enter an attraction, while others will climb over the railings to avoid paying for a festival or concert. Some will slip items into their bag in the supermarket or not scan all items at the self checkout. Others deliberately place items on the counter in front of a shop assistant ringing up the items, so one can't really be seen and then justify it by saying the shop assistant made the mistake. Some people fake tickets or ID so someone can get a better deal. Some buy online to obtain discounts they don't qualify for. Some people lie to schools about their children being ill when they are going on a term time holiday. Some people might not be perfect, but try not to do the things mentioned above.
People have a choice about how to behave. Some are more desensitised to how their behaviour impacts others, some are more selfish and interested in themselves and others have a broader view of society and other people. We could all do with being more honest with ourselves about our own behaviour.