Howdy folks,
As far as checking the value of a specimen plant by asking at a
nursery. A lot depends on which nursery you ask. The mark up for the
same plant ( often from the same grower ) can vary a great deal from
nursery to nursery.
When I worked in a retail setting folks would come in to find a
'value' on their plants for insurance purposes, after some sort of
accident, ( painters trashing their gardens, cars out of control) and
of course they would get quotes from the poshest places in town and
avoid Home Depot.

Most nurseries are not interested in consignment plants, for one
thing a certain percentage of plants is just not going to make it long
enough to be sold, and you don't want to take an eight foot fica on
consignment and then have to explain to the owner why it suddenly lost
all it's leaves. For there to be an economic incentive for the nursery
owners the plant owner would have to match wholesale prices, and the
plant owner would likely be shocked as to the the difference between
the wholesale price and the 'value' of the plant.

Finally if you are a nursery that sells $200 dollar Ficas, your
customers are either furnishing out an office, or are high end
interior designer types,or folks who are more interested in instant
gratification and appearance and are willing to pay for it ( I once
had a set of parents from Dallas who stopped into the greenhouse to
pick up $800 dollars worth of large houseplants to spruce up a dorm
room at UT for their daughter who was starting her freshmen year that
weekend.) Folks like that are hard to reach unless you have the
convience and name recognition of an established business.
I would suspect that most gardeners ( like myself, or the kind of
folks who wade through the detrius on this forum ) prefer smaller
plants that they can nurture along themselves which for me is what
gardening is all about. Part of my enjoyment of the eight foot plants
I do have, is the knowledge that I raised them from gallons, or four
inch pots, or even cuttings.

Eighteen years ago I had a house with forty houseplants, some
being Philodendrans in ten gallon containers that reached the ceiling.
When my last child was born I decided I could change diapers or take
care of houseplants but I wasn't going to do both, so that Christmas
everyone I knew got a houseplant with a red bow. In addition to
streamlining my life it helped save me a lot of money to pay for the
diapers.

take care,
Steve Coyle
www.austingardencenter.com