But surely you understand that it's often a matter of people's disposable income varying and what they choose to do with it?
Even NMW is £1700 pm so a couple of low earners working full time will have nearly £3.5k pm coming in. If they're experienced professionals, their household income could be double this or more.
Not everyone has huge outgoings. You've said most of the group are child free. So no childcare, holidays in term time at a fraction of the cost and only food, clothes etc for 2 people. Their mortgage might not be that much if they've bought some time ago, inherited, bought as singles and combined their equity etc.
Our basic bills for direct debits, food and petrol are under £1k pm so it's not impossible to see how a childfree couple can save £1-2k pm.
Plus a lot of people spend a lot of money on discretionary items, so if people just don't spend this money, they can save more.
Have a look at where your money is going and be honest about whether the amount could be reduced. Do you have a car on finance? Is your broadband more than £25 pm, your mobile above £10 pm, do you get your hair coloured? Nails? Other grooming? Pay TV? Do you have takeaways, buy lunches, coffees, gym membership? How much do you spend on eating out? Are you always 'doing work' on your home or buying new furnishings or decorative items? Do you have a cleaner? Do you spend more than £5/600 pm on groceries? Is your holiday expensive? Do you have pets?
Every one of these you've said yes to is a use of money that could be saved instead so to save more you need to spend less (or earn more) so it's a matter of different people having different priorities.