I was speaking to my fiancee about this last week after a member PMed me some questions.
He said that slabs all cost the same, varying prices is because your paying for the quality of the stonemason, and unfortunately many volumne builders are focused on the money aspect.
Joins should NOT be extremely visible. If I saw a join such as VJ's I would be extremely disappointed. Talk with your stonemason before your kitchen is ready and be adamant with what you expect. It can be done to a better standard.