Not long ago there was a discussion of these and their quality on a bulletin board I frequent. It was either here, the Bear Mountain bulletin board, or the Wooden Boat Forum. You might want to do a search.

As I recall the consensus was that getting two bits for $40 was about as inexpensive as you could get. There are more expensive bits from other suppliers. Presumably the quality is better. Mac McCarthy notes that the cheap ones are OK for a boat or two, but if you're going to do more you might want the more expensive ones.

I purchased the Woodcraft set for less than $40. These are also sold separately for about $22 each, so make sure you order the set. They are from Taiwan. The ones from Woodcraft have 1/4" shanks.