I got trays made for my mouth and teeth whitening paste from my dentist about 4 years ago. I believe it was about $300-$400. It might be less now. I think the most expensive part is getting the trays custom made.
I've used the Crest White strips, you can get them from Walmart, K-mart or Target. I can tell you that this product worked for me 100%, I use them and my teath are SOOOOOOO much whiter, Good luck!!!!