The thing is, authorized centres simply loot people purchasing laptops by charghing them 2-3 times the cost for upgrading RAM, HDD etc. This culture has been there before companies like Dell arrived on scene and allowed people to upgrade their laptops.
If you ask me, it's worth taking the chance of upgrading the unit yourself especially on low end laptops. RAM and HDD generally easily replaceable and are always a compromise on the low end.
Also, the value of a low end laptop is not much as the build quality, screen etc will also be compromised. So, It does not make sense spending more on upgrading a low end laptop at an authorized service centre. For the money they charge you, getting a better laptop in the first place makes sense if the cost is reasonable.
Also, does anyone take the extended warranties on offer? I was offered a 2 yr additional warranty for 6K for my Compaq celeron based lappy. I'm glad I did not go for it cuz today, it's not worth much and I'm always worried about what they would actually cover in the event of a problem.