The clubs are currently in talks over a deal but while Leverkusen accept the 23-year-old is likely to move on this summer, they will not let him go on the cheap.
Bailey, who scored 15 goals in the Bundesliga last season, has emerged as one of Villa’s top targets as they look to bolster their attacking ranks.
Boss Dean Smith also has a serious interest in Burnley’s Dwight McNeil and it is thought Villa are prepared to make one more big-money signing.
Goalkeeper Marcus Bettinelli, last week linked with a move to Villa, is set to join Chelsea.
Villa are on the lookout for an experienced shot-stopper to provide competition and cover for No.1 Emiliano Martinez following Tom Heaton’s departure.