I don't have any suggestions for you, but I can tell you I paid about $100-120 for mine last year here in Northeast Ohio. I may have been able to shop around, but I like this nursery (not big box store), I like the people who work there (year after year it's the same people), I've liked every other plant I've purchased there, and I was buying other things that day, so price checking just wasn't worth it.

I see them consistently at local plant nurseries so check a few of those too to see if they carry them where you live.

Here, tree-form hydrangeas run about $120-150 at any better nursery. But they are not the tiny little things I have seen posted here purchased from one of the box stores. They are 5-6' tall and with a fully developed crown. It takes time to achieve that size and maturity with a tree-form shrub and you are paying the grower for that time and effort :-)

btw, the box stores around here never offer anything like this. They just can't compete with the selection and customer service offered by the independent plant nurseries and only provide very basic landscape items and annuals. It may be different in different parts of the country.

Be patient. Many retailers don't begin carrying hydrangea paniculatas til later in the season. As most H P's bloom later in the season, they tend to carry them while they are in bloom or at least just about to.