There are two issues:
1. horticultural practice (were they the right trees and were the properly cared for?
2. blueberries are notoriously screwed up. There a couples of major types (rabbit eye, northern highbush etc.) and multiple varieties within each type.
You have to plant 2 different varieties adjacent, of each type.
And you have to pick the type that grows well in your climate.
The trees were started and grown at a nursery 20 miles from my house here in NH. They were not brought in from another state. That is why I bought them there.
There were grown by a nursery where the owner went to the UNH for nursery/horticulture management. They are trees specifically for the NH climate.
My point is they take 5-10 years before they produce very much fruit. Macintosh apples are $.99/lb at the grocery store. Honeycrisp are $2.99/lb. Cheeries are $3.99/lb.
Do the math.
I have two different types of blueberry plants. Planted in rows about 8’ apart. They were growing for 20+ years on a farm about 30 miles from my house. He had 3 acres of blueberry bushes he was plowing under. I paid $20/plants that were 3’-4’ tall.
So, I am into these plants for $140 plus peat moss, fertilizer, etc.
You can buy blueberries for $3/pint at the grocery store. I need to grow 50 pints of blueberries just to break even.