To clarify both my comments and yours:
You can certainly sell something for more than you paid for it, but this is not 'profit'.
To be clear as to the reason for this, HMRC make this distinction, you have referenced the badges of trade and one of the badges of trade is the 'intention' to make a profit, and another references length of ownership. The nine badges together can indicate whether trade, hobby or investment activities are taking place.
A trader will buy or make, or improve items, generally in quantities, that he expect to sell, generally quite quickly, for more money that it has costs him, including all the costs involved. That is profit. Obviously the timescales are determined by industry but one does not set up a business without the expectation of profit at some stage.
A person can buy something for an investment or for use and, absolutely, that item can be resold for more than was paid, but that is not profit, it is realising the investment.
The difference between trade and investment is that, when trading, the expectation is to make money, to profit from sales activities.
An investment is only hope that the asset can, at some indeterminate time, be sold for more than was paid, with the realisation that this might never happen, that it can increase or decrease in value, all outwith the owners control.
Of course a toy from the 1970s can increase in value, but most of the toys from the 1970s were bought to be played with and almost all were broken and thrown away. Very very few would have been bought for investment, and the buyer would have had absolutely no idea what their toy might be worth 50 years later, so the motive for buying was for the enjoyment of use or, perhaps, for investment. And something can be bought for enjoyment and become an investment.
While your 15p matchbox toy might be worth £100 today, it might be worth £80 or £120 next year. How did anyone know which one to keep in the 1970s? Some are worth thousands today (and not just the pristine, never been played with, never taken out of box items) and some are worth 15p.
Problem is 'profit' certainly is the term used - rather mis-used, for selling something for more than was paid for it. For tax purposes though, profit refers to the amount of money a trader has earned from ALL his buying and selling activities, not just because he bought something and sold it for more money.
If, as a trader, I sell buy 1000 necklaces at £25 each and sell them individually on eBay for £50 each with free postage, over a 12 months tax year, then I've sold them for £25000 more than I paid, but this is not profit. If my listing costs were £3500, and my FVFs were £4500, buying costs £25000, my postage costs £5000, and my business overheads and £5000, my profit, at the end of 12 months, would be £7000.
If, however, I only sold 70 in that tax , and promoted them all at 5%, I would have made a loss. Even without a profit this is trading, as I would have had the 'intention' of making a business profit. (Though making a loss too often could lead HMRC to determine you are not a trader, particularly if you continually offset losses against your other tax liabilities).
Determining whether something is a hobby, an investment or trading determines which tax laws do and do not apply.
