There are two online stores - spherehobbies.com and aeromodelsupermarket.com (sharma aero models) who have ready stock of balsa sheets.
Now for 1.5mm ( or 1/16") spherehobbies has 3" x 36" sheet priced at 97 per sheet, while sharma models are charging 223 for 4" x 36" sheet.
Now, even if we factor the different size, the cost differential is huge....

Can anyone explain this to  me?

Origin of the Balsa could also be a factor - where is it from - Ecuador/Colombia or Indonesia/Thailand?

The Sharma blasa is very light and very soft with very even grain.... the other one.... well its a no no for me.....

siddharth models from thane

Are you looking for bulk or retail?

well the easiest way of making dowels is....
1.   Use metal rods for place of dowels usually Aluminum is used for this.  Even Brass would do the job equally well.
2.   Get some bamboo pieces and use a sturdy knife to make your own dowels of 4-5 mm dia.... they are equally strong and just as good.... if you have any fear of them breaking make them of about 6 mm dia.
Well I have used Bamboo dowels stated here all my life..... and they have never failed me yet. i.e. over 25 years of aeromodelling.

Dear Dynamite,
Just go to the local market where construction material is sold.............. tall bamboo poles are used for support during construction of buildings.... best ask your local maid or your local office boy he will get you a one foot long bamboo which will suffice your needs... 

have you seen indian bush which have long long leaves just get into it cut one from the bottom peel it you will get it
or go to wood shop say
"i need border for board door"
choose the white one it is very much similar to balsa just little heavy but much much hard