Toothpaste is one of those things you have to buy and you can still get reasonably cheap toothpaste (I've yet to see any of the supermarkets do a value version though!) however, if you want to go for one of the branded toothpastes, whichclaim to help you out of sensitivity hell, then it can be expensive to try them only discover you don't like the taste or they don't work quite as well as you hoped.
I don't have sensitive teeth but I got swayed by a Sensodyne Pro-Enamel advert one day (because of the enamel promises), it wasn't cheap and after a few days my teeth had become sensitive! Needless to say I didn't carry on using it and had wasted a few pounds in the process.
If you'd like to try Colgate Sensitive Pro-Relief toothpaste for free then click the link above and just wait for it to arrive in the post.
Thanks to notts6501 at HUKD