Vests represent the "voting power" you have...
The more STEEM you have powered up, the more voting power you will have. However the actual value of your vote however depends on two things completely out of your control!
Total number of vests
If a lot of people power up or more people have accounts, your relative voting power falls! Since I started here almost a year ago, I have seen my 100% vote value drop from $ 0.43 to$ 0.13 and now back up to $ 0.15! I completely overlooked the fact that even if STEEM appreciates, the vests will suffer heavy inflation! If I wanted to keep up with "vote inflation" I should have tripled the money I put into STEEM or be more successful: I failed on both counts :[
the dollar value of STEEM
The higher the price of STEEM, the higher the value of your vote! Nice an easy!
TL;DR
The value of your vote depends on your *relative *voting power and the STEEM price. Over time the voting pool expands and there is a huge inflation, but hopefully this will be offset by a sharp rise in the price of STEEM!
What do you think about the "vote inflation"? Do you care?