The complete series is not seen very often and the first 10 covers are rather scarce.
Several of the first 10 are available on eBay
currently, including 3 listings for #1. The prices asked for #1 can be a bit excessive, as there is an offering on eBay
right now for the full 100 covers for the same or less than is being asked by two of the listings for #1.
I have two complete sets, bought as such. I am working on a third, buying them individually, just for the challenge of accumulating a set that way. I probably have 90 or so, with a few of those without the inserts, so I am always keeping my eyes open for replacements with the inserts. This third set, accumulated individually, will no doubt end up costing at least 3-4 times what I paid for the complete sets.