I'm hoping there are some bike riders on BB who could help me...

DS needs a new bike so I thought I'd get him one for Christmas. I went to the bike shop where I found a bike reduced from around $300 to $200 ish, which is pretty much what I wanted to spend. The woman told me it was a 'cheap bike' and not to buy it because it wouldn't last him a year, she said I should spend no less than $500 .

I know nothing about bikes. My mum is an avid rider, her bike is probably worth more than my car so she agreed with the sales girl but I just can't justify spending that amount of $ on a bike!

DS is 13, he rides his bike to cricket training (about 4 km each way) 3 times a week on both the road and walking track. The bike he currently has is a tad too small so he's been riding DH's, hence getting him a new one. I thought a lower end bike would be ok for that He also goes on rides with DH once or twice a week and will ride to the shops on occasion so the bike will be used a fair bit in the warmer mths but not so much in winter.

Seriously, do I really need to spend $500 on a bike for a 13 yo with the amount of riding he'll be doing? I'm so torn, on one hand I don't want to buy a piece of crap but on the other hand I don't want to be wasting money on a bike that's not going to see the year through or on a really expensive on which won't get used to its full potential.