How old is Yankee? A few months ago I had a 9 month old male neutered that only had one testicle and my vet charged around $130. While I agree that he should be neutered I think his age should be a factor in your decision. Here is an interesting article that speaks of the increased risks caused by having them neutered too young.
http://www.naiaonline.org/pdfs/LongT...uterInDogs.pdf
Sometimes you just have to go by your gut feeling and trust your puppy buyer. To me the utmost concern should be the welfare of the dog.