Quote from: jiijj1 on June 22, 2017, 12:34:09 PM

currently the fee is around 2usd for priority, there is a ICO that I want to participate in, if I pay 10usd as fee I get first in line in mined block to guarantee participation?

is there any disadvantage with having 10usd fee, maybe the transaction get cancelled?

any difference playing 2usd fee, 10usd fee, 100usd fee?
the biggest fee gets first into the mined block?

Usually, yes, the more satoshi's per byte you add, the higher the chance a miner will pick your transaction above the other transactions in the mempool. However, it's completely up to the miner. If the very next block gets mined by a miner that choses only to include the coinbase transaction, your transaction won't be added... If the next block is mined by a miner that decided to fill the block he's working on with spam transactions, you're also straight out of luck.

However, generally speaking, if you outbid the other transactions in the mempool, you have a really big chance of getting into the very next block.

There is no "downside" for using "to high" fees... Exept the fact that you'll pay more fees (obviously) Wink

That being said: there are two more things i wanted to tell you
1) there is no need to outbid 100% of the waiting transactions in the mempool... Study https://bitcoinfees.21.co/ for more info, but what i mean to say is: if you pay enough to be in the top 1Mb of waiting transactions, you'll probably get into the next block.
2) be carefull: fees are not calculated per transaction or per amount of BTC transferred, but they are calculated based on the transaction size. This size depends on the number of inputs and outputs...

You can use my tool to guide you in picking a good fee: https://www.mocacinno.com/page/feeestimate or you can rely on the fee estimation of a DECENT wallet...