It seems to be £4.50 per publisher per year, not per visit. There are roughly two visits per year. I don’t know how the finances of COs have worked up until now, but on the face of it this seems to be an attempt to move at least some of the financial burden away from the branch and onto the congregations. If that’s what is going on then I think it could easily backfire. What Watchtower never seems to take account of, when asking for more money, is that publishers, as rational consumers, are perfectly capable of simply deducting whatever extra they pay out for an extra fund from what they would have donated to the general fund in the first place. So they may get their extra £250 or whatever CO fund from each congregation, but find that contributions to the general worldwide fund goes down by a similar amount, and they are back to square one. In fact if donation solicitation fatigue sets in, then contributions may actually go down over time.
It certainly seems to me that contributions to the general worldwide fund have gone down over the years. With all the extra payments Watchtower insists upon, and the discontinuation of literature, I guess many people simply don’t see the point of the world wide work contributions box any more. What Watchtower takes with one hand they lose from the other.