I'd imagine Phillips would not be cheap, somewhere between 5-7 million, maybe more. The reason I think this is that Holloway has been talking about him as the next big thing for quite awhile now, so clearly rates him as one of their best players. Blackpool also were very sensible with the PL money they got from their short time in the league, plus the parachute payments they are receiving mean that they probably do not need to sell to buy, and they weren't a million miles away from getting promoted last year, so any club would have to pay a premium to get their best players.
This is obviously all just guess work by me and could be miles off