The $7.99 USD price for that Evanovich omnibus is indeed slightly cheaper compared to the $2.99 USD sale price on the 3 individuals, assuming one isn't going to “travel” for a discount on the exchange rate which would make the lot cheaper overall. (And it shouldn't have been compared to the CAD price in the first place, which was entirely my mistake for not even noticing that I'd entered the wrong set of numbers in my post, which makes a lot more sense if you actually save some money versus the individuals instead of spending 2 cents more, which is what a CAD purchase would have actually cost.
)
And even in Canada, its existence at what seems to be a regular stable price at an equivalent amount enables one to hold off on buying the individual sale books in it, which SYKM says are fairly far up the series timeline, so one could technically save a bit of money by skipping those for now and hoping for a further pricedrop on that and #15.
In any case, it's an excellent series sale, and I hope it does well enough that Macmillan are encouraged to offer more for the further volumes in other authors' series beyond the usually discounted #1.