Runes of Magic US / AU

Unique crafting-furniture in the item shop (under Housing-Crafting) is available (diamonds-only) for production-crafts. They give a crafting "bonus" when placed in your house, but just how much help is this bonus? Is it worth the cost in real-money? This "bonus" supposedly helps you level-up faster by:

1) Increasing percantage skill increment for every completed item. How much?
2) Reducing the time to craft an item. How much?

Has anyone calculated how this bonus translates into actual improvement? For example assume that crafting a given sword normally takes 30 seconds and gives a 2% skill increment. How much will a 50 point bonus affect these numbers? Does the 2% increment become 2.1%, 2.5%, or 3.0%? Does the item crafting time decrease to 29, 25 or 15 seconds?

Stackable or Not?

Are the several different furnitures in the item shop for each craft stackable? Blacksmithing for example:

Blacksmith anvil: 50 bonus, 35 diamonds
Cooling furnace: 10 bonus, 9 diamonds
Branded anvil: 60 Bonus, 45 diamonda

If I get ALL 3, is my Blacksmith Crafting Bonus now 120 (50+10+60)?

This would be even better for Tailoring:

Cloth Cutting Table: 50 Bonus, 35 diamonda
Spinning machine: 60 Bonus, 45 diamonda
Weaving machine: 70 Bonus, 57 diamonda

180 Tailoring Crafting Bonus if these 3 stack. Do they?
How come Tailoring gets more total bonuses then blacksmithing (180 vs 120)?

I would greatly appreciate hearing from those who have bought and used this crafting furniture. Is it worth the cost in real-money? Just how much improvement do the various bonuses provide?

Since no one else was able to provide an accurate figure, I finally did
the research myself. If you're afraid of a little algebra - STOP NOW!

• OLD = the percent improvement for crafting a single item at crafting locations outside your house
  
• NEW = the percent improvement for crafting the SAME item inside your house
  
• BONUS = the sum of all bonuses of all nearby crafting furniture. Bonuses are STACKABLE, but must be RELATED. For example, Carpentry projects will NOT receive any Bonus from Blacksmith furniture.
  

then the formula is

NEW = OLD * (1 + BONUS / 1000)

Example: Assume you get a 1% skill increase for crafting an item outside your house and
you have two pieces of RELATED furniture, one with a 70 Bonus, the other a 60 bonus.

New = 1% * (1 + ( 70 + 60 ) / 1000 ) = 1% * 1.13 = 1.13%

With the crafting furniture inside your house, you get a 1.13% skill increase.
So, instead of needing to successful craft 100 items to level-up (100/1),
using crafting Furniture inside your house only 89 (100/1.13 and round up)
successful crafted items are needed.

It's not a big change, but it is significant. In addition, it takes noticeably
LESS TIME to craft each item, but that's harder to calculate exactly.
If and when I do so, I'll add it into this thread.

WARNING: ONLY the owner of the house receives any BONUS.
Visitors allowed into the house may use the furniture to craft, but
do not receive any bonus. This is not stated in the Item Shop or
any description of Crafting Furniture I have seen. Visitors do see
the BONUS given in the status box of the house and may therefore
expect to receive the BONUS, but do not receive any BONUS.

I believe the BONUS should apply to Visitors allowed by the owner.
Or this limitation should be CLEARLY STATED in the descriptions of
Crafting Furniture, along with the "Guild Castle" limitation. IMHO,
having unstated, "hidden", limitations is at best bad business practice
and deceptive.