I've had some great luck over the last couple years but nothing fantastic in the last few months.
My best score was getting these, along with a lot of other nice stuff in an album for $65:

I tend to stay away from dealers or regular stamp sellers while treasure hunting and look for sellers just trying to flip something they got for a profit without researching. It does happen.I look for a couple of telltale signs that there "might" be something really nice and it's not just a kid's collection from the 70s. I also grab things that turn people off because of high shipping charges due to weight. I was once the winner and 2nd bidder on a 45 pound box of albums, sheets and other nice stuff for $50 because the shipping was $45. Think it had over $800 in face value mint modern US alone and the seller never added it up before. Most of my collection has been built this way along with a few individual stamp purchases.
I've even started collecting worldwide since a lot of the old albums/lots I buy that had nice US stuff, many times had very nice foreign stuff as well that I just put aside for a rainy day