Chojubai is a lovely cultivar of flowering quince. Recently there have been some spectacular photos beautiful of very old Chojubai in Japan, and a couple articles in bonsai magazines and blogs on them. This has rightly re-kindled the interest in this cultivar. It is lovely. It doesn't have to be expensive, I bought a 2 year old cutting for only $12, Spring 2014. Of course a Chojubai with 25 or 30 years of growth and ramification will be roughly 10 to 30 times the price.
All the reasons listed in earlier posts about it not being easy to handle in an in-ground nursery setting are reasons older specimens are pricey.
There are other cultivars of flowering quince that have most of the nice traits of Chojubai, that might be more affordable for older specimens.
Keep a look out for Chaenomeles 'Hime' and Chaenomeles 'Kan Toyo' both have small leaves, 'Hime' leaves can be smaller than 'Chojubai', and they both ramify very nicely. They are both dwarfs, much like Chojubai. 'Hime' is a nice orange-red with small flowers, Kan Toyo has flowers in white, pink or white and pink much like a miniature version of 'Toyo Nishiki', yet 'Kan Toyo' leaves and ramification are similar to 'Chojubai'. Out of bloom you could not separate young specimens of the three by growth habit. The only negative for 'Hime' and 'Kan Toyo' is the fact that their bark stays relatively smooth, like most other cultivars of Chaenomeles. They do not get the rough bark that 'Chojubai' gets. This is not a big negative, because the bark of a 'Chojubai' is not very noticeable until the tree is near 20 years old.
So there are other desirable cultivars of Chaenomeles out there, the "focus" on 'Chojubai' is almost cult like at the moment, but if you can see past the bark, there are many good cultivars of Chaenomeles to choose from.
My favorite is 'Chojubai' but I also love and keep 'Hime', and I have the larger growing quinces 'Toyo Nishiki' and 'Iwai Nishiki'. And in the middle size range I have red contorted, white contorted, and a cultivar Brent Walston (Evergreen Gardenworks) named 'Not Minerva'. All are lovely in their own right.
photo attached of a 2nd year cutting of 'Not Minerva' in a 4 inch diameter pot.