If you're saving $4/domain and you have a big portfolio, that is enticing. Saving $20K is probably worth the hassle of spending a day or two transferring domains.
Some have offered the first year discounted, but force you to pay the second year up front, at the regular jacked up price - which obviously doesn't make it worthwhile most of the time.
But if this is a legit no strings attached one year transfer, then it is indeed pretty enticing.
Unfortunately, I just did $15K worth of upcoming renewals a few days ago...