[DOC] add economics of gas

[amgando]

Gas price evolution over time

Prior gas price * 0.0001ish then total gas spent in the previous block / gas limit - 0.5.

No, it hits a hard boundary where it can’t fall below. And we expect that it’ll stay at the minimum because most of the time blocks will be less than half full.

In the future when they add shards, the goal is to keep it that way anyway by adding new shards if the blocks are getting too full.

https://near.org/papers/economics-in-sharded-blockchain/#transaction-and-storage-fees

[amgando]

consider the following alignment between gas and staking proposed by @nearmax
near/NEPs#67 (comment)

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The general idea behind staking is the following:

• We want someone to perform operation on our blockchain, but while they do it they are given a great deal of flexibility that they can use to abuse the system. In case of validator staking validators can produce invalid blocks, in case of gas staking the users can arrange shard congestion by submitting tricky transactions;

• We however are not able to prevent it, either because the computation is too complex (in case of validators we cannot run BFT consensus because it is too slow and expensive) or not possible (in case of transactions it is not possible to predict what receipts user's transaction will create);

• So we solve it through staking -- we require the actors to loan the assets that we fully or partially return after they have completed their interaction;

What is new however, is that we previously though of stake slashing as a binary situation that only happens when actor misbehaves and it can be directly proven. With prepaid gas, the misbehavior is not only non-discreet but also it cannot be attributed to malice, so we "take away" part of the stake (if we could prove malice we would've taken all stake).