I'm not sure I ever know the budget, but I do tend to design towards what I know will be the expected practices.
Some of those details are in how the bunkers are raked, and how their edges are to be maintained. And that depends on the equipment. Some may want to mow bunker banks and edges at speed, and most bunker bank mowers can now turn on their 10 wide blades, meaning bunker noses need to be at least 20 feet wide, or a bit more on slopes. If they have a 10 foot wide mower that can back down slopes, and don't mind doing that in part or in whole, then a bunker nose 9 feet wide works okay, since they at least limit it to one back down per nose. Most will accept a few exceptions to a rule.
In reality, even when designing a course where the proposed green fees are above $100, the super rarely says, "I don't mind a difficult to maintain area, so have at it." Even those who tend to accept it, have found that their course, built in the go-go 90's or early 2000s, change their attitude a bit in the next big recession, where budgets are held or cut slightly. And, I have seen older courses that went through WWII and the depression simplify things, and now that I have some courses that are up to 35 years old, I see most of those have softened bunkers and what not to reduce maintenance cost over time. In short, it raises the interesting question (related to the "formula design" thread, or do I design what looks great new, or do I design to something that it will probably morph to for maintenance costs?
So basically, the comment about designing to 75-90% of the expected maintenance budget is probably right on. And more than that, it's designing to existing equipment and mowing practices, unless I am 99% sure the facility will always remain a high end club.