Oliver Kahn believes it is a matter of time before Paul Pogba's EUR105million transfer record is broken and fears Bayern Munich might struggle to keep up with their Premier League and LaLiga rivals if fees continue to rise.
Manchester United made headlines when they broke the EUR100m mark to lure the France international away from Juventus and back to Old Trafford ahead of the 2016-17 campaign.
Kahn thinks there will soon be a player who costs in excess of EUR150m, although he is unconvinced Bayern are willing to go that far.
"Huge amounts of money will have to be spent in the war to sign the best players," Kahn told German football magazine Socrates.
"I think the EUR150m mark will soon be broken.
"It will be a huge challenge for Bayern to sign players of [Franck] Ribery and [Arjen] Robben's calibre in the future.
"The question is whether Bayern are willing to go along when the English and Spanish really start spending big in the years to come."
Javi Martinez remains Bayern's record signing at EUR40m, although Portugal international Renato Sanches could end up costing them up to EUR80m depending on a number of conditions.