On this day last year it cost £601. No matter how you calculate it, it is a HUGE increase!
Yes, it is a huge increase, but on this day last year, a spousal/child dependant visa cost £885.
A spousal visa hasn't been as cheap as £601 for several years - it was £515 in 2008 and up to £750 by 2011.
But that third time will hopefully be their application for settlement visas (since that'll be the 5 year point), so there won't be a fourth! I know there's a 10 year path too but I haven't looked into 5 year vs 10 year differences yet.
By the current fees (which will obviously keep increasing), you've got:
First visa, valid 33 months = £1,195 + £600 NHS levy = £1,795 per person
Second visa (FLR(M)), valid 30 months = £811 + £500 NHS levy = £1,311 per person
ILR visa (permanent residence) = £1,875 per person
UK Citizenship after gaining ILR = £1,236 per person
So, in total, based on current fees, you're looking at £6,217 per person to get to citizenship.