I am looking into Bitcoin mining, and want to ask if I have done my Math correctly.

Bitcoin mining difficulty increases by 20% every 2 weeks.

Let's say, I make 1 BTC over a 52 week period, without taking difficulty into account.

In order to take difficulty into account, is the following correct....??

1. Take 1 BTC, divide by 26 = 0.0384615384615385 BTC every 2 weeks

2. Take 0.0384615384615385 ... and multiply by 0.8, to take into account the 20% decrease.

So....

1st 26th = 0.0384615384615385
2nd 26th = 1st 26th * 0.8
3rd 26th = 2nd 26th * 0.8

and keep going until

26th 26th = 25th 26th * 0.8

Is this the right way to do it??

Is there any way to predict the time to mine a block?

On Ghash.io, I've seen blocks mined in a few seconds, a few minutes, up to as long as around 2 hours.

This seems highly unpredictable, but is there any way to predict it whatsoever.

I was thinking about going through 1000s of blocks, and seeing how the average block time changes over time, e.g. what is the average for the last 10, 100, 1000 blocks, and if at any point the average becomes in the same, in which case it would be predictable.

But I haven't done that yet.

So, does anyone know if it's predictable, and if so, what is the average block mine time?

OK... I got a response from XtremeMiners support team, as to why they sell ASIC miners...

We actually don't use the machines to mine for ourselves because it would destroy the bitcoin concept if one company has too much power over the currency (that's why butterflylabs and other companies sell as well) and also, we are all about spreading the idea of bitcoins, we want people to use them, and make bitcoins popular, to support the bitcoin project. That's why we provide them with miners.

Personally, I think that this is their BS excuse, rather than telling me that you're simply not going to make much money from this, if at all.... and that they make mores selling the ASIC than they would make from mining.

What does everybody think?

Right... but, according to minr.info... there is an ASIC that makes $397.40 per day, and takes 26 days to break even... After that, you would make $397.40 per day in pure profit.... and the total price of the ASIC is $ 9,995.... so... within a few weeks after break even, you would have made more than the total price itself....

So, I can only assume that by then, mining difficulty has increased so much that you're no longer making $397.40 per day...

Is this right?

Why do companies sell Bitcoin miners, like ASIC?

Surely if they can make money from mining, they would keep it themself.

The only other option is that they make more from selling it, than they would make from mining with it.

It's definltely not some charitable gift to the people.

So, what do you all think?