Hi Hyaku,
Anything that is new technology is expensive. Red LEDs have been around for many years and therefore are cheap now.
If you buy 10 blue LEDs, ask for a quantity discount. You should get them for about $8.00 or get 2 more free.
Small diodes used to be $1.00 but are $.10 each now. Resistors used to be $.02 each but are also $.10 now unless you buy a lot. ;D