Make an estimate and go to the first line to enter an item. Type the name that you want to call it and hit tab. If the item is not yet set up in your system, it will ask you to set it up. Go in, give it a name, price, markup price and distributor (if needed) and save it.
Next time you are making an estimate, type in the name again, it will pop in automatically, price, description, and everything. It will show you a quantity, price per item, subtotal, markup, and total line per item. Only you will see the cost price and markup percentage that is automatically calculated from the difference between your cost and your markup price to customer.
So... when you print out the estimate for the customer, it will show your 5 gal plant, 20 of them, for 25.00 each for a total of 500.00. Put in all your other items for the job and skip a few lines down towards the bottom. Enter an item as "labor, install, man hours etc... something like that. Estimate the hours it will take to complete the job, put that in at your labor rate. It will add that in as well to your grand total. Pass it on to the customer, tell them "LISTEN UP, ESTIMATE ONLY, THIS COULD CHANGE IN EITHER DIRECTION." if thats the way you fly.
Like clark said, make into invoice once you get started on the job and your almost there. Quickbooks is pretty good. Im looking into Microsoft Small Business Accounting 2006, looks pretty decent. Dont know if it has the estimate feature or not. Good luck