Top said:
Bottom line, they lie about the bonuses pure and simple. Oh, and check your math. The increase I see is only 16.6% not 25%. The increase should be consist across the board and it is not.
The item increases the gathering speed by 50% of the base amount. But it's also increased by your dominion lost art. So depending on what level that is the relative increase you get may be different from someone elses. Also remember it's an increase in speed, not a decrease in time. This applies to almost all boosts in stormfall. So if you build the gathering/building/research speed by 50%, this makes the new time 1/1.5 or 66% of the old time, not half. a 25% boost would be 1/1.25 or 80% of the old time (again, not counting the fact that the boost is a % of the base value, so if you have other boosts the total effect will be less).
This may seem arbitrary, but there are certain reasons plarium does boosts this way. For example, look at boosts to unit power. Lets say you have 10 different boosts that give an average 30% boost each (this is about what's actually available, some are larger like 50% some smaller like 10% but averaging them makes the math easier). If they all apply to the base value, then this gives you a final power multiplier of 1+10*0.3 or 4.0x the base unit power. So that means your dragons will have an offense of 6720. Now lets say each one applied to the final value of the previous ones (ie your units already have boosts bringing them to 4k power, adding another 30% boost gives you 5.2k). This means the same 10 boosts averaging 30% each would give you a multiplier of 1.3^10 or 13.8x. so your dragons would have a total power of 23184. So for offense/defense boosts it makes sense for plarium to apply them the way they do. I'd assume they just apply the boosts to other things such as upgrade/research/gathering speed the same way for program consistency.