As for the normal pros- most of them gets what ever is the best graded and looking bats available to the manufacturer/Supplier, or they allow the player to pick from their collection.
But I am not so sure about what the star sponsored players like Kolhi, Dhoni, Smith or Root etc are getting.
As many sponsors like to send out 6-8 bats to the player to chose from to play with. In which some could be stunning looking bats and some could be extremely average looking bats.
Some supplier like to send 2-3 bats based upon the availability of a cleft deemed good for a pro player
For sure they are getting the cleanest bats with no visible blemishes(Which is a marketing thing for the manufacturer), but I am not sure about the straightness and number of grains. Have seen big stars playing with wobbly grained bats.
For a pro-bat all the controllable factors(right from raw cleft, weight, balance and finishing) are optimize to produce a master piece with all the major and little details nailed to perfection.
But my point is why cannot the manufacturers/makers can use some scientific method to determine the performance of a bat (As baseball bat are determined by BBCOR rating system).
This will allow the customer to make a more informed decision in place to picking something with no guarantee of performance.
Currently the bat market is like going to a shop and buying a mystery box.