I'd say it depends what you expect of the kit. I've got an Oregon Scientific for about £100. Does the job perfectly well for a 'snapshot'. Change the batteries more often than you strictly need to for best results.
Tracking using data from Manc airport shows it's as accurate as I need - moment to moment accuracy is irrelevent in most cases anyway, with the exception of windspeed. For that sort of money you can get something that follows the trends pretty well.
The Davis kit is expensive for a reason - it records about as accurately as you'll get for consumer kit. As said already, it would need to be sited well to make use oif it's ability - not a straightforward job in some cases. If you want to max it you'll need to be pretty handy with software also.
Handheld units are quite an interesting option (if your into weather more generally). Take one into a typical British thunderstorm and you can get some surprising results.
