James is correct, the cheapest way to get accurate pH results is to use a soil lab, you will get more information than just pH but that is also needed for blueberries.
In the chemistry/ biology world the words Accurate and cheap do not go together.
Accurate can be listed in varying degrees, so the first question would have to be "how accurate do you want to be?"
If you want your own pH meter this is very valid question since 0.0 accuracy is less expensive than 0.00 or 0.000 accuracy.
Most labs will give 0.00 results across the board.
For you to buy an instrument that accurate you will spend around $150.00 + another $75.00 -$100.00 for the calibration solutions, glassware, pure
water for rinsing/storing the probe.
Redhawk