fun situations can arise when you write , instead of ; For those not in the know, in c++ the comma operator evaluates the left expression, discards the value, then evaluates the right expression and returns the value. if you now have a a situation like this
int i = 0,
printf("some message");
i has a completely different value, since it actually uses the return value of printf instead
presumably this graph shows the buying price, discounted or not. going by that, the site probably adopted the regular price as the "sale price" and inflated the non-discounted price. after black friday the promotion ended and the price returns to the "old" value.