The NASB and NKJV editions of The MacArthur Study Bible
are $6.99 at all of the usual suspects, including Kobo. They're coupon eligible, so 50% off with BookRiot50
for a final price of $3.49.
If you're a fan of the NASB, this edition has much better formatting than any of Lockman's electronic editions, so it's easily worth buying just for the NASB text. Also be aware that the study notes are nearly identical between versions (differing only in quoted Bible text, as far as I can tell). If you have it in one translation, the only real reason to get another one is the convenience of not having to switch while reading.
NASB: Kobo B&N eChristian Christianbook Sony Amazon
NKJV: Kobo B&N eChristian ChristianBook Sony Amazon
The MacArthur Bible Commentary
is $6.99 as well. Though modestly updated, this is essentially the MacArthur study notes without an accompanying Bible translation. Again, eligible for coupon codes at Kobo.
Kobo B&N eChristian Christianbook Sony Amazon
I suspect that the sale may be to bring attention to the very recently released NIV version of The MacArthur Study Bible
that is currently $33.99 at Amazon and Kobo (and more everywhere else). It's coupon eligible, though, so if it's worth $16.99 to you, knock yourself out
. Just make sure you enter the coupon code before completing your purchase.