This is how I only spent RM6 for the above birthday cake for my 3yo son.
I bought a butter cake from a cake shop that cost only RM6. Then I used the left over buttercream icing from last week birthday party to decorate it. And the candles, you can get it free from the cake shop when you purchased the butter cake.
And I got a happy birthday boy. Hey, all a kid wants is candles to blow and cake to "chop". And the best part is, my birthday boy get to decorate his own birthday cake. =D