Accepted Solutions
Can I piggyback on this?
All properties a Machine Resource can have should be available to Custom Resources... including cost and LEASE. 
I haven't gone too far into trying to figure-out/set either of them, but I can see value in having both. (It looks like "cost" is a dead end anyway if rszymczak doesn't have it working... heheh)
Yeah... I was talking about something different... but in a way the mechanism could be the same.
On the back end of a machine resource item is a cost, and I think we should have a way to set it directly based on programmatic changes. We can SET the cost now... As you noted, the current way to set it is through the three mechanisms (maybe four due to blueprint daily cost?) that you mention.
(With regard to blueprint daily cost... maybe you could have tiered blueprints, and if something changes... e.g. Bronze level to Gold level... you move the machine itself to a blueprint with a different blueprint daily cost? Not sure if that would work... Just a random thought...)
Here is a vRA plugin inventory item... used to illustrate what I think you are asking for, which might help me as well.
For example... if I were to ever get really fancy and start giving out databases as a service from a shared database farm (not a db server, but a db itself). Perhaps I would want to inventory those custom items in ASD/vRA during the request (web server, app server, backend db). Well there is a cost associated with having a database that includes storage and hardware/licensing share. If I have a table that I maintain with the costs, and one were to request a database as part of their environment/multi-machine request, I would need to be able to add that cost to the business group's total costs. It would be helpful if I would have a place on the resource item to PARK that daily cost, which gets calculated over time as the total cost for the *custom* item.
From what I have seen of it... I imagine that vRBM Advanced can add costs from external database sources. So I could have a completely different tool for costing out database instances and then aggregate the data between vRA and the other cost sources using vRBM. But for me, what I described above sort of makes sense as a logical extension of what is already being built out in the vRA product and associated vRO plugins. Custom resource items have those properties... but they are not used (hasCosts is false... hasLease is false). Doesn't seem to be much of a leap to expand the product so that they may be used. Nor does it seem to be much of a leap to add in a custom costing property which could be leveraged for both Machine and Custom resource types.
I dunno... maybe I am not making a lot of sense. Maybe it would never be utilized. (I guess it would depend on how well it was implemented, and how many people have custom costing requirements.)