We didn't visit any Denver shops, but we stopped in Idaho Springs and visited a shop near us in Summit County. First off, yea you can buy concentrates.
The first place we stopped was called "Strainwise" where we picked up some Grape Ape shatter and some Green Crack crumble.
We also grabbed a tootsie roll type thing. The tootsie roll was 100mg and KICKED our asses the first night. I had maybe 1/3 and my son ate the rest.
The concentrates tasted great in my Persei, but there is some question as to how well it was purged. See, it had bubbles in it, but I could not detect any butane taste. The grams were $30, which turns out to be 1/2 the price of the other place we stopped at in Idaho Springs. I can't remember the name of the other place, but we grabbed some yummy Swedish Fish. They had nice buds but they were like $25 per gram. No thanks!
High Country Healing is the shop in Summit County (Silverthorne, I believe). Their shatter was $75/gram! That's even more than we pay here in RI. We passed and instead grabbed some candy bars, a soda, and a gram of bud ($18) that was pretty good.
For recreational users, it seems that most places sell you a "mix" when it comes to concentrates and edibles. It was hard to find a straight up indica that I wanted for sleep. The edibles were pretty racy, it seems. I mean instead of falling asleep, I was spaced out and almost tripping. Much different from the ABV edibles I make, LOL! I would also think medical prices are better, and prices in Denver better than the places I went.
I mailed my Persei and Pax home instead of taking them on the plane. I also mailed the leftover concentrates, 2 grams of shatter, and some more edibles. My package is on the truck and will be here this afternoon. I am looking forward to really inspecting that shatter for purity, etc.