Once my initial buying craze was satisfied and I had dialed in what I liked and what I didn't, it became a bit easier. Once my appetite for general variety was appeased, I then started to focus on individual acquisitions (i.e. a certain scale material, maker, either vintage or new, etc.). Once I had most of those materials in the collection (though 1 notable material is still absent), I began to focus on pure value...so there is now really not ever a need to over-pay. I still have a number of things on my list, but I can wait for them to get the value I feel necessary to make the purchase. There are also some individual razors I am willing to pay well for, given they are in the right condition.
Fact of the matter is that if you are willing to pay, you can have virtually any razor instantly. If not, a little luck, good timing, right place/time is needed.