So you are completely ignoring all the other essentials I mentioned like clothing and utilities. Lovely.
You seem to be getting a little tetchy.
Also you are the exception not the rule in this case.
You pay VAT on things like alcoholic drinks, confectionery, crisps, savoury snacks, ice cream, soft drinks and mineral water.
Maybe those things make up a large part of your shopping basket but for many people they don't.
Basic rate taxpayers are only getting 68% net
You've taken no account of the allowances for Income Tax or National Insurance.
At £50k p.a. you receive 75% net
At £40k p.a. you receive 77% net
At £30k p.a. you receive 80% net
At £20k p.a. you receive 86% net
however you need to consider that we pay 20% VAT on most essentials like clothing, only basic food items are exempt. So it's more like 54% net in the UK for basic rate taxpayers.
You've reduced 68% by 20% to get to 54%.
Let's look at our £50k earner. Their net pay for the year would be £37,664 (75.3%). Assume they spend all £37,664 on items with 20% VAT that's £31,386.66 plus £6,277.33 VAT.
£6,277.33 is 16.67% of £37,664. 75.3% reduced by 16.67% is 62.75%.
The majority of the food we buy is zero rated for VAT. Gas and electricity attract 5% VAT. There's no VAT payable on domestic water charges.
Let's assume our £50k earner is still spending every penny of their income but at an average VAT rate of 15%. That's £32,751.30 plus £4,912.70 VAT.
£4,912.70 is 13.0% of £37,664. 75.3% reduced by 13.0% is 65.5%.
For our £20k earner their net net pay for the year would be £17,264 (86.3%).
Assume again they're spending every penny of their income at an average VAT rate of 15%. That's £15,012.17 plus £2,251.83 VAT.
£2,251.83 is 13.0% of £17,264. 86.3% reduced by 13.0% is 75.1%
So it's more like 54% net in the UK for basic rate taxpayers.
Admittedly using some quite rough calculations but following your assumption of 100% spending and reflecting Income Tax, NI and VAT then 65-75% is closer to the mark.