Hm, I'll need to recheck this when I get back. You may be right and if so I'll update the article.
*¤&%&%&!!!
I just spent three hours writing a full response, and the browser crashed. *sigh*
OK, here we go again, luckily most of the work was in validating the numbers...
I checked again, and you are wrong. However, by forcing me to recheck everything, you pointed me to a mistake I had made in my first model. I'll explain that and post the updated numbers, but let me first explain why you're wrong, and let me do so with the extreme example you had.
In my model, I am deducting the dividends earned by the competing contracts from the prices of contracts currently mining. This means that in the analysis, any dividend earned works in favor of the competitor. I believe you mentioned this wasn't fair and that one couldn't compare minig with a non-mining asset, but you may have misunderstood the model as it already accounts for this.
However, If difficulty goes up 1 million percent then no dividends will be earned at all, so no price deduction takes place.
Of course, this also means that everyone loses everything, so the question really becomes who pays more for their shares because that determines how much an investor will lose. Because BFMines is priced lower than competitors per mhs, that means investors lose less with BFMines (they would lose 0.00468 with TAT.VM and 0.00400 with BFMines).
To be accurate, this depends on when the difficulty goes up by a million percent. If that happens next week, then dividends earned until next week will reduce the loss.
To err on the site of caution, for my model, I have actually assumed that no difficulty changes happen in July at all. This favors competitors, due to the balance between the BFMines bonus being lower and the decrease in reduction from the competitors, the effect isn't too great (a percentage point or two). If I include the changes during July, it favors BFMines.
Now to my error.
In my first model, I had wrongly reduced the dividends by the same rate as the hashrate increase. In other words, if hashrate increased 15% then dividends would decrease 15%.
This is obviously wrong, because if the difficult went up 100%, the dividends would then be zero, when they should be 50%.
In the fixed model, I now correctly use the growth in difficulty to calculate the returns. Although not entirely correct for a physical mining operation, I have used the formula from DMS.Mining, as I'm sure you'll approve of that being correct (or at least equal for all).
I should mention that when designing the contracts, I used the correct method.
So, the results...
My statement from the article is that the chosen difficulty shouldn't affect comparing the assets 'too much' (only mining investments in general). The 'too much' is of course a relative term, so let me show you what it means in practice.
Here are the results from the updated model using 15% as the monthly change:
Here are the results from the updated results using 30% as the monthly change:
As you can see, the change from 15% to 30% affects TAT.VM competitiveness by 1% point only. This is due to the reduced price reduction countered by the reduced bonus. I'm thinking this is within the limits of what you can call 'not too much'.
The overall effect on mining profitability, however, is reduced by just over 14% for
all assets.
I had spent a long time describing the formulas before my browser crashed, and I can't be bothered to rewrite it all again, so I've uploaded the Excel sheet to Google Drive so you can verify the formulas yourself.
https://docs.google.com/spreadsheet/ccc?key=0Am7kSNaxKrIMdGg1WnI1ZFp2RTh1ZXp2NVpCNkxIVGc&usp=drive_web#gid=0I should point out that if updated with today's prices and the reduced dividend payout time for competitors until September 1 (still not accounting for price drops), BFMines is again the cheapest mining investment per mhs on BTCT:
This does not include any transaction fees, however, which would further favor BFMines by a percent or two, depending on what the transaction fees are. Of course, if the transaction fees goes through the roof, that further increases the benefit to BFMines contract holders, as unlike TAT.VM at least, the dividend is based on real mining rather than a return formula.
Speaking of which, and slightly off-topic; does DMS.Mining pay out transaction fees?
The effect you mention with your extreme example slightly affects the analysis if the increases are within normal expectations only, but the effect is so small that I call it, with good conscience, 'not too much'. For a doubling from my chosen numbers, the effect is around 1%; for a quadrupling, the effect is another percent.
However, from there on, the effect is turning around and is eventually cancelled out, so if there's an increase of 240% per change, BFMines is faring better again, and with a change of 1 million percent, the effect is all but cancelled out. In other words, BFMines, with its lower price and bonus is effectively priced at the same level as TAT.VM was when I wrote the article.
With the price rise on TAT.VM today, BFMines is the cheapest mining contracts on BTCT, regardless of whether you include any of the factors that would further favor BFMines.
.b