The sale ends on June 15th according to whoever manages Logos' Twitter feed. I contacted sales by WebChat on June 2nd to find out the end date. Firstly, they said they didn't know about the sale!! They then told me it was for the whole of June. I even took a screenshot in case the sale ended earlier and I needed to try to ask someone to let me still buy at the sale price, because my credit card statement date is mid-month. I wasn't totally convinced the guy in sales knew his facts, so rather than risk missing out, I sought approval from the "bank manager" and ordered the books that were at "amazing prices" - arguing I was saving $80. I'm sure I've heard that argument before!
The main point though is that it looks like the sale ends June 15th.