Condition Expectations

I recently purchased a 1972 Topps partial set 755/787 that was advertised as "NM" for $728. The description indicated that the set was EX-NRMT with 10% lesser.

The set arrived today and as I was going through the cards I noticed water damage on several cards (including nearly every star). After noticing the damage I started going through the cards very closely and found well over 100 with clear water damage and a solid 100 more with discoloration from likely similar exposure.

***water damage is significantly more offensive to me than normal wear.

I am generally reasonable and expect to find cards that will need to be replaced when I purchase a set/lot. I do not get upset because a few cards slip through below grade.

In this case, I opened a return to send the set back. I felt that if I kept the set I would likely be finding more damages for the next year and ultimately end up having to replace many more as I looked at the set more closely over time.

Where do others draw the line on this type of purchase?