As an admin you may have noticed that the hardware tier cost in the hardware tier definition under admin>>advanced>>hardware tier does not seem to match what is presented to end users when they select a hardware tier to use on a workload. The difference occurs because the hardware tier definition for cost is in Cents per minute and in the end user settings in the project UI settings is in Dollars per minute.
As an example note the "small (kubernetes)" hardware tier definition below. The cost per minute is 0.00020 cents per minute.
Notice here though in the launch new workspace UI, the cost per minute is $0. This is just the cost in cents, 0.00020, being converted to dollars $0.0000020 and then being rounded to 0.
Although the cost is not actually $0, the cost of this particular tier is so small that rounding to $0 for user purposes is a fairly close approximation.
Note that this is just an example and many tiers are not this inexpensive.