Your are saying this because his not an England player, if he was an English player you wont say 100million is small for such a talented striker like Viktor, how much did Manchester city bought Gealish from Aston villa was it not 100m, so Viktor worth 100m too, any club that can pay should pay and get him, I know Arsenal won't pay such amount for him, so Manchester united is at advantage because Amorim can convinced him to join Manchester united with him as his former coach, Manchester united has a chance to sign him than Arsenal. But Manchester united won't spend such amount on him, they will negotiate the best price.
Viktor Gyokeres is the main target for most of these elite EPL clubs next summer. The scouting and sporting directors of these perspective clubs have started making moves towards the angle and possible links with the current Porto attacker, Viktor Gyokeres. Manchester United might have good probability of landing this player next summer because Ruben Amorim who happens to be his former coach is already getting intouch with him and we can possibly tell how this thing will play out among these parties.
Arsenal sporting director, Andrea Bertha is doing a good job but yet to land specific target for his players. Gunners are eager to bring in new players because obtaining a title will need them go extra mile to get hands on potential players.