It depends on the circumstance.
For example, I personally would not buy the X-Men omnibus because I think it will get a second printing soon enough
but would fork over $200 for the first Hickman Avengers omnibus, because if I buy volume 2 at IST for under $70 and the
second for $200, that would end up costing me an average of $135 per book, plus it is probably a safe bet that Marvel
will not be re-printing volume 1 any time soon.