We are doing a bunch of these for a wedding this summer. I'm usung a 40 inch tall vase (rental) with a 4 foot manzanita branch balanced across the top (also a rental) The hanging orchids are not that difficult...we wire them at the shop, take it all to the site, and assemble each arrangement in place. Pricing is difficult, because your prices and mine are probebly not the same, but for me, it is 6$ per cymbid blossom,
15$ per phaleonopsis bloom, 25$ rental for the vase, and 40$ for the manzanita branch. The ones I am making also include haging votives, so I add that cost on too. Then I figure out how many man hours on site, (including loading and driving time, and driving back to the shop etc) and add that as a separate line item to the proposal.
Manzanita branches are crazy expensive here...wish I could figure out something as strong, but cheap, that I could find locally.
If the cost is too high, an alternative is to hang dendrobium orchids...way cheaper, but still nice.
Hope this helps.
Joanne