It is ok if you are satisfied. Bu I would not spend such an amount on periodic maintenance. If something goes wrong I think that the repairs/replacement of such parts would not be that expensive.
For example I changed stock plugs at 32K km when I went for CNG installation in 2008 (after three years and they were checked cleaned just twice at 3S), the second replacement was done on Aug 1, 2010 (58,300 km) though there was no problem, plugs were replaced at Shell pump near my house where I got oil change. I buy filters, plugs from Toyota genuine parts stockist in Rawalpindi (Hamza Younus Autos) which is way less than the prices of 3S.
Breaks: So far have been services twice, no replacement needed. Will go in next few days for a check and if needed replacement would only replace breaks.
I think only companies can afford the detailed maintenance recommended by 3S dealers or IMC or Toyota. Even if essential maintenance is done at 3S you can still have a trouble free ride. Many maintenance jobs which do not require sophistication for example, alignment, balancing, washing, plugs change, oil change etc can be done in open market.
My friend has clocked 91K on his 2006 Xli, for the past two years he is going by road to Karachi from Islamabad without any single issue. Same break pads he has. He also goes to 3S for breaks, fluids replacements and has no issues with his car. He is not satisfied with the level of expertise and way of handling repairs, maintenance at 3S. He says they do not have common sense.