if you created your own altcoin.

you would then need to make that altcoin work. need to mine it so that blocks are produced.
because you are just one person. with one cell phone. your altcoin wont make blocks for a long while. it would take months and years for all them missing blocks to trigger difficulty drops sufficiently enough for your cell phone to start mining a block successfully and frequently, so that you can make a payment to yourself or someone else.

by that point if you could get someone to be part of your network. they too could mine. and they would then value the altcoin based on how easy it is to acquire your altcoin by different means.

so if you were trying to offer your altcoin to them for $40k. they would decline because they are at a cellphone mining speed too, meaning 0.01c to mine fresh coin. so why would they want your $40k coin, when they can mine on your altcoin network for much less
because they may not want to go through the effort of mining they might go upto 0.02c or they may think about making their own altcoin and see the time and effort so they may go upto 0.03c, keck they might offer you 0.04c rather than 0.01c to another altcoin making person who doesnt have the same features. because the features(you copied from bitcoin) have more utility then someone elses altcoin missing the features.
but its the combination of features and costs of utility that build up a valuation..
..
now do you see why i mentioned the mining value stuff many posts ago.
now do you see why i mentioned the ease of use factor many posts ago
now do you see why i mentioned the features many posts ago
now do you see why i mentioned the benefits many posts ago
now do you see why i mentioned the utility many posts ago

its a combination of all factors

your altcoin might have the same features of protocol. but it lacks other features, like its acceptance by retailers like its mining cost, like its ease of use, even things like your altcoin is only mined by 1-2 entities meaning the centralisation risk of it is high, making it less appealing

right now there are dozens of ripped off altcoins copying bitcoins same protocol. depending on a combination of many factors that make them atleast viable to be used by some and not used by others, and the cost associated with it differ depending on different mining costs. and also the ease of use with others and retailers make some of those rip offs vary in price. some from as little as a penny. some for a few hundred dollars. but none come close to genuine bitcoins value because bitcoin can do more then what the rip offs can

EG
they/you are not buying the serial number of a bank note.

if you had a bank note and decided to copy it(counterfeit) retailers wont accept it. if then you try to convince someone to accept it, they would have to evaluate the cost of your photocopy vs their own ability to photocopy. and their own risk of retail acceptance. and in the end they might offer you a penny for your counterfeit bank note.

or they would look at a genuine medium of exchange that has actual costs involved and ease of spending. and just use that one
even if the ease of use the genuine medium of exchange comes at a higher cost. because of its utility and features that make it better than the issues, headaches and risks of your silly altcoin/counterfeit bank note