You only think about Bitcoin in the context of investing because of the profit and the price, which is the main factor, but Bitcoin is actually much more than that.
Totally agree, that's one thing I often say in these threads.
I bought and spent BTC when it was only worth a few hundred $, and I do the same today.
This is another thing that I think hits the nail on the head. In the vast majority of the cases of the people that we met bitcoin years ago, it's not like we bought a large sum and waited for the price to go up without doing anything. The most normal thing is that at the beginning when you didn't know it very well you bought a little, and then you sold some when the price went up, but if you have done well over the years you will have maintained a positive trend of accumulation despite buying at some times and selling at others.
It's rare not to find a bitcoin user who hasn't made profits via bitcoin. The argument has to do with greed, earning too many profits. As you said, you bought at a smaller rate and sold during a time of a bit price increase. Somehow, we all have been through it, made a few bucks out of bitcoin, which we didn't labor to earn. Contrarily, all bitcoin holder has lost a few bucks in bitcoin according to the accumulated bitcoin. The regret arrives when we begin to see the bigger picture of bitcoin and the profit potentials of bitcoin, if we don't sell a single Sat. But, that doesn't matter as Lucius said; the technology is quite deeper than the shallow price trends attached to USD. Many hodlers don't sell regardless of the trend; bull or bear. A significant illustration of the power of bitcoin, as a currency, not an avenue for generating profits.
So, purchasing a product we once owned at a higher price than what it used to be, doesn't occur only in bitcoin. When cars were first invented, it was cheaper than what it is today. However, we can argue this in the form of inflation, as the old price has almost a similar buying power to today's price. Associating such ideology to bitcoin we can easily attest to the changes of bitcoin price as an increase in trust. When the price was cheaper, in a few $100 investors didn't trust bitcoin, with their money, that's why they didn't accumulate up to 20BTC. While those who did, sold it, because of personal real-life situations. Which is normal, and not a problem. Remember 20 BTC then should be around $2000, still a significant amount of money 10 years ago. In my country, 2000$ then was about $600 in value via purchasing power. I'd comfortably say that $600 10 years ago is worth $2000 today. Due to a change in dollar value. Since the dollar is highly inflated the price of bitcoin to dollar per BTC will continue increasing.
It doesn't remove the fact that 1BTC = 1BTC. The difference in inflation contrarily to bitcoin is that the value of the dollar decreases. The person who holds $600 10 years ago till date won't get any reward for hodling such an amount in fiat. But, $600 worth of bitcoin 10 years back is about 6 btc at a rate of $100 per coin, if I'm not mistaken. But the person is certainly rewarded with close to 200k USD. Hence, the price is huge enough to beat the inflation, giving back the investor a profit worth more than he invested. These statistics and calculations in price increase leave an average bitcoin investor or scholar to think they've missed on a golden opportunity. But, bitcoin opportunity doesn't come once, it's here looking at everyone interested in investing. It's still very cheap according to Lucius's response. The same year the price dropped below 20k dollars and now the reward is doubled and still increasing. In simple terms, bitcoin is a money that provides a huge interest but is highly volatile. It's better to save money in a bitcoin wallet than in banks. So, the profits associated with bitcoin, aren't the reason why users shouldn't trade their coins for fiat to settle bills. Sometimes we can run out of savings. Those who don't will be rewarded handsomely for saving money in Bitcoin.