Absolutely no chance the fee would be remotely close to Hackney. Hackneys the best midfielder in the league, Peck is a long way off that. He’s a good young player with a very good ceiling, but he’s nowhere near the top 5 midfielders in the league. Also not saying he won’t get there though.
With some proper coaching and patience he could be bottom premier league/top of the championship easily, but as others have said, it’s hard to say what he actually is, he’s not a monster in the middle of the park, he’s also not a free scoring midfielder that provides assists and goals. He's a bit of a jack of all trades, master of none. With a modern approach to coaching, I think he’ll find his niche and do well.