Let’s suppose a dApp needs 8GB RAM to support its userbase and the developer has 1000 EOS tokens. Can the tokens be used as RAM by staking or would she have to buy RAM separately? Later if the project does not take off as expected and the developer chooses to shut down her dApp, will the price paid for RAM be refunded/returned if sold?
In short, if 1000 EOS tokens are spent/staked to get 8 GB RAM, when 8 GB RAM is sold/unstaked what does the developer get in return?
Buying/Selling uses the Bancor algorithm to sell the limited supply at market prices and buy it back at market prices when it is not needed anymore.
Market prices will be impacted based upon speculation, actual demand for RAM, and increasing capacity provided by block producers.
According to Dan Larimer, in Dawn 4 RAM can be bought at the current market price. If, later on, the RAM is no longer needed, the developer can sell the RAM at the then current market price. Depending on the state of the blockchain, the developer may realize a profit or a loss on the sale. There is also a 1% market fee involved in these transactions that goes to the BPs.
Please read Introducing EOSIO Dawn 4.0 where it is explained in details.
The TL;DR is that RAM will be bought and sold at market price (but that's an oversimplification - you should refer to the article).
