These StewMac kits look good but start at $75.  At least you know they won't be garbage and you can get any missing parts replaced. $50 kit from unverified web retailer not so much...

StewMac Uke kits

We bought 3 ukes in the $100 range.  

A few years ago we taught a uke class in our homeschool co-op.  The families bought $25 amazon setups and put good Aguila strings on them.  They sounded great and the geared tuners held up well.

If you're just wanting any uke for a  teen to fool around with, any concert or tenor sized uke with good strings will do fine.  The biggest thing for it is geared tuning pegs and good strings.