Metallica is way more expensive.
In an interview it was confirmed that Iron Maiden was the most expensive act at Graspop, later Rammstein and GNR Reunion surpassed that. Aerosmith often asks for a lot, but the price falls through in negotiations.I know this from a very reliable source.
Aerosmith also had increasing difficulty selling out the large stadiums, which the band is used to in the USA.
Tool wasn't on GMM yet, but I can't imagine that band being more expensive than either of the above.
Aerosmith is struggeling in sone countries, but the others dont. Tool was in the lift, but I think they are at their limit