Having had interest for bitcoin among all altcoin, I tried to imagine if the price of bitcoin is reduced to atleast 80% so that It can be affordable, and before this is done a proper warning is sent to all the users and holders so that they can sell before time to avoid lost on their part and buy back when it is stable and relatively cheap.
It sounds like you’re imagining something unrealistic, and no serious investor would want that. If they’re looking for cheap investments, they can go for altcoins, but Bitcoin’s system and progress should never be changed just to make it more affordable.
Also, calling Bitcoin "expensive" isn’t the right way to look at it. Unlike a physical product with production costs and a set selling price, Bitcoin's price is purely driven by demand. Even if you see it as expensive, there are still investors buying at the current price, and they’re not stupid. They do it because they believe it will still be profitable in the long run, knowing that Bitcoin’s price will continue to rise over time.