return their investment to where.. maybe you should learn bitcoin. there is no central company called bitcoin..
you never pay "the bitcoin system" to purchase bitcoin in the first place. because thats not how currency works. its not how bitcoin works.
(random people mine it and sell it. other random people buy it)
can you atleast try to make the distinction of of you want to think of bitcoin as a asset(analogy: product) or a service(analogy: retailer) and stick with one.

thats the brilliant point of it. you never get your coin from a central company. its always a currency you get from people. those people could be direct face to face or using an agent /exchange that is the middleman service.

you do know what currency is right.. its a medium of exchange..
the purpose of currency is that it does change hands. meaning it is exchanged for something else of value deemed reasonable to the parties involved in the exchange.

if you want some 14 day return policy of 'if your not completely satisfied with your purchase then send it back to us and we will refund you' go buy some btc from someone that has this extra customer satisfaction condition.
not all retailers give products a satisfaction returns policy. and that does not make the product a scam.
products do not come with satisfaction aftersales service as standard. its upto the seller to offer it. not the product

infact. i have sold BTC to people and a few days later they have changed their mind and i accepted their btc back and gave them their money back at the original purchase rate.. so to answer your question.. yes someone can return their investment without funds contributed by new investors..

you just have to find the right person to get the coins from that offers such a customer satisfaction returns policy..
retail products dont come with satisfaction returns policy as standard. its upto the retailer to decide if they want to offer such a complimentary aftersales services.

oh and by the way..
not all corporations 'buy-back' shares on demand. you might want to research fiat investments while also learning about bitcoin utility/function/economics.

but i do laugh.. if you ever thought people can just hand their shares back and get 100% refund at anytime.. then you will find out the hard way, that shares dont work how you think they work

go on i dare you.. buy 2 shares of TESLA at (time of post) $704 each
and wait for the price to drop below $704. and then try to hand them back to elon musk and ask him for $1408.. i guarantee you he wont give you it.