This isn't necessarily a myth, but it is a question I'm interested in. What determines the exact value of a room? There's some info on the wiki here but it looks like some of it is out of date.
Anyway, I came up with a theoretical list that all you bored mythbusters can attempt to verify.
I think the value of a room is broken down like this:
- The sum of the values of all furniture.
- The sum of all floor and wall tiles as follows:
- For unsmoothed, natural floors and walls, the material value of the floor or wall is added.
- For smoothed, natural floors and walls, the material value is multiplied by five, and then added.
- For engraved, natural floors and walls, the material value is multiplied by five from smoothing, and then multiplied by the quality modifier of the engraving, and then added.
- For constructed walls and floors, the material value of the building material is multiplied by five and added.
For furniture adding to the value, as far as I can tell, the answer is "usually". Every room I've ever made, the furniture's value has added directly to the room...except when the room is 1x1 over a bed, in which case its value is only half that of the bed (rather than the bed's full value). For instance, if I base a 1x1 room on a -bed-, the value will be 10, rather than 20.
I eventually got fed up with trying to come up with an equation, and gave up on it. Hopefully somebody will have the patience to get it all figured out. Also, I haven't tried with multiple overlapping rooms though and haven't tried with non-bedrooms (i.e. tombs, offices, etc.).
And yes, the wiki is thoroughly out-of-date, so much so that it's just plain WRONG.