So when adjusting Falcon Manor recently, I decided to take advantage of a feature that didn't exist when originally creating the Manor, which is a count of the total number of coins.  This would have worked differently before it was possible to reach every room in the mansion, but now I think of it as a neat little feature that if you get 100% score, you'll have a nice round number (i.e. 40,000 points.)

This is particularly easy to do if you just load up the final (treasure) room(s) with coins and money bags until you reach your desired total, as long as you remember to edit it again later if you make changes earlier in the mansion.

The point of this thread is not about even numbered point totals, though, it is more to do with coins/money bags throughout a mansion:

How do you decide how much of a reward players should get while playing through a mansion?  Do you just play the game and see how many lives you think you need, and add some more?  Do you just add coins where you think it would be nice to have coins?  Do you go for a specific reward/room or reward/death trap ratio?  And how does your expectation of the intended difficulty level for a mansion affect this decision?

A tough question, indeed.  My short answer is:  All of the above.  Really.  I try to take all these factors into consideration while building.  That said, the factors that matter most IMO are the difficulty of the mansion and a reward for solving a problem.