Not everyone in this world change blades very often, and also
NOT everyone use razor blade!
we can assume that this earth is equal, means we have 50% male and
50% female.
then we categorize them into 5 cat, A (from 0-20yrs), B (from
21-40yrs), C (from 41-60 Yrs), D (from 61-80yrs) and E (80 &
above)
People now can live until average of 67 years old.
So only category B, C & half of D need to use razor
blade.
It's just 25% people need razor blade in this world. But 100%
people on Earth need toothpaste & toothbrush and
syampoo!!
But look at household consumables item, even when you are just a 1
month old baby, your mom have to wash your clothed and change your
napkins. At the same time, your mom & dad have to clean the
house & brush their teeth and etc!!
So, you actually consuming consumables item even when you are 1
month only!!
When you get old, even if you have no more real teeth (maybe due to
insist of using non-sugarfree toothpaste), you will still use
toothpaste to brush your fake teeth.
You start brushing your teeth from yr 1 to the day you die, but if
you are a guy, you start to use razor blade when you are 20.
Can you see the difference between razor blade & consumable
item?
If you wanna compare with computer parts, can!! let's talk about HP
printer.
in a HP LaserJet printer, there will be many parts such as heating
elements and etc. Although HP printer is very famous in the world,
but HP is the only company on Earth that produce heating elements
for HP printers.
But let's look at toner & cartridge, a lot of remanufacturer
toner and refill cartridge running in the market.
Why these competitors do NOT want to produce heating elements and
they start to bang the toner market?!
This is because to a printer, toner is a consumable item and
heating elements is just a spare parts. Consumable item will never
ever be saturated BUT if they start to produce heating elements,
they will be in deep shit.
cheers! 
