1m is what Kubo would of agreed in wages per year with us, with no transfer fee attached.
Hiroki doesn't look anything special. Let's see where they both stand in a years time and which would have been a better 1m investment.
Let's assume Hiroki will get the same wages we've reportedly offered to Kubo (250k). If he'll stay here for 3 years that's 750k in wages. With 1,1M initial transfer fee 1,85M in total costs. Kubo would sign "for free" but he'll earn 1,25M/year at Madrid. In three years that's 3,75M or twice as much as in Hiroki's case.
Also, Kubo is more an offensive midfielder or #10 while Abe will probably be used as a winger which we currently lack in Barça B.
They are both long shot to make it to the first team but I don't believe people would actually be so high on Kubo if he would be just a random youngster from J1 League without Barça past.