The price of Steem and VEST are related. The VEST price will change then accordingly to the market price of Steem, to keep showing the right amount of Steem Power, because that is what it represents.

If the price of Steem goes down and the VEST price would not compensate for this, then the amount of Steem Power would drop visibly. And the only thing that does drop visibly is the virtual value in US$.

But, every minute about 720 new Steem gets created that gets distributed under Steem Power owners. This is still considered Steem related in value. So 1 Steem Power growth per hour has still one Steem to back it up in value.

This value has to be kept at the same level of Steem Power. Even when the value of Steem is dropping further and new Steem Power gets added. So, the value per VEST will change, rise even in the price of Steem stays the same, because more Steem gets created, that get added as Steem Power. That needs to be revalued in VEST.

And this is an ongoing proces, because the network keeps creating Steem that becomes Steem Power, that is represented as VEST at a blockchain level. And this VEST amount has to be valued in such a way that it shows the right amount of Steem Power in an account's wallet.

This would also mean that the value of 1 VEST could only drop clearly if the price of Steem would rise enough to compensate for the amount of Steem created every minute.

In conclussion, Steem Power will still be worth the same amount of Steem in a Power Down, as Steem will be in a Power Up. Even though behind the scenes it represents a higher value for VEST, that is still the same amount. But with a different ratio, to get the right value for Steem(Power) all the time.

VESTs can not be directly traded, they could be seen as only excisting on a blockchain level. And the value, or multiplier that is used for it, is to keep the right amount of Steem Power represented. That needs to be able to be Powered down to Steem at some time.

So, as far as I see it, it's 'value' serves mainly as a multiplier to keep the 1:1 balance in value between Steem and Steem Power.

If an account holds 104.000 SP and Powers Down it still will get a 1000 Steem per week, for 2 years. No matter what the VEST multiplier is set at.

The challenge then would not be the VEST multiplier, but the continues creation of about 800 new Steem per minute. At least that is how I come to understand it.