What is the cheapest pulse oximeter I can get?

Quantified Self General Health
1

http://www.google.com/search?q=pulse+oximeter&num=100&hl=en&prmd=ivnsr&source=univ&tbm=shop&tbo=u&sa=X&ei=tUFpTu_fCsjKiAKVx9WhDg&ved=0CI4BEK0E&biw=1920&bih=1084

Are the more expensive ones better in any way?

2

I saw one for $30 at Walgreens last week! The expensive ones have data logging capabilities which are quite useful.