This is something I have never understood the logic behind the statement. Additionally, I truly believe the Model-A Hobbyists are the biggest users of this statement.
How many things in life are truly worth what we must pay for them? When we purchase a brand-new vehicle (Car, Truck, Motorcycle, Boat, RV, etc.) from the Dealership, the Market-value is what we paid for it however 15 seconds after you made the purchase, that item is no longer worth what you just paid for it ...yet look at how many of that particular item is purchased each & every day. The same applies to us purchasing Groceries, Clothing, or other household items. The price you paid was Market-value yet as soon as you own it, it is no longer worth what you paid for it, ...yet we knowingly still make those purchases. If I want to go to a fine restaurant to eat a nice steak dinner, I do so realizing the next morning it will not be worth what I paid for it on the previous day!!

The list just keeps going on.
Now applying this to collector vehicles (-and more specifically Model-As), name a Model-A restoration shop that does not have multiple customers on a waiting list to have their Model-A restored. Name any quality restoration shop in this country that does not have a waiting list. That is because these Hobbyist are not concerned with "Market-value" or '...it'll never be worth what you put into it.' or whatever. Just like any items previously mentioned. If I want a new vehicle, I realize that it will not be worth what I am paying yet I/we make these purchases anyway, -yet we can't/won't spend money on a Model-A.
I am a firm believer
THIS idiotic mindset is what has killed or is killing the future Model-A hobby. I cannot begin to tell you how many nicely restored Model-As that I have seen or worked on that were actually driven into the ground by the (previous) owner because they would not spend money on maintenance. The reason, ...the mindset that "I am not going to spend money having maintenance done because I'll have more money in it than I can get out of it." How many Forum posters have given the advice to buy one already restored instead of restoring one? Most 'restored' Model-As on the open market today all need major work simply because they have been used/abused to the point where they are unreliable. Even the insurance companies have a low value on the Model-A because they too realize that the overall state of the average Model-A is a worn-out, used car. So how have we as Model-A ambassadors been good for the hobby touting this mindset?