Hi pplchl,
It's true that many factors have to be considered when buying such an expensive bag. Alaska has a point - it depends on your child's character too. If he doesn't treasure his things, money will really be wasted if the bag is used for a short period only. As for changing of new bags at the beginning of each year, we can change their pencil cases, water bottles instead.
I had to get this bag because my son's school does not permit parents beyond the drop-off point. He has to climb 'mountainous' stairs to main compound, and then another 3 levels to his classroom. He's also on school bus home, so there's quite a lot of walking & climbing (x 5 days, x 4 weeks, x 9 months)!
I have seen the SPI bags....they tend to be rather heavy as the 'spinal' support is built into the bag structure. There is this hard piece of plastic to support your child's back & waist. But I think they have lighter ones too. Yes, there are other brands and different price ranges too. More important is for you to check them out; let your child strap on the bag (preferably with something inside) & walk around.........see if he's comfortable.
Maybe I'm biased but I tend to like the LEGO bags very much! You can visit the LEGO shop at Ngee Ann City, level 5. Or the children's section at Takashimaya.
Having said that, it is really
not compulsory to get this type of bag. If your child's school timetable is not so packed or if your child can make use of his locker well, an ordinary bag will do.
Good luck on your shopping. Enjoy the experience....it can be quite bonding for you & your child!