One of my first wins on ebay 11 years ago was 16 sets, mostly very large sets (kids often want sets, not bulk) for $200. They were brand new, and half the list price. I gave some every Christmas and birthday for the rest of their childhood.
;)
THAT is a good deal. I saw one bulk sale of 70 pounds of Lego (yes, 70 pounds); it was a combination of about several dozen sets.
I like your idea of buying several complete sets and gifting them over a long period of time; that is efficient! How did you keep them hidden until it was time to wrap them?