Assuming that the Bey itself is mid at best in terms of competitive use, what would the rough pricing be for a Prize Bey out of a Random Booster be expected to be? 

As bad as it is, I'm hoping that Shark Edge that drops tomorrow won't be super important in the metagame, and be a reasonable price. The purple variant looks so much nicer than the yellow one.

they’re usually not too bad if you can snatch one right away. They tend to shoot up in price for awhile after that then come down later. Specific price really depends on the bey and how sought after it is.