In Canada:
duplication.ca can be very pricey. The quality is okay. From what I've heard I wouldn't use them for anything other than cassette duplication, if at all. Did one tape through them (tapes only, got cases and covers done elsewhere) and never plan on going back. (MASS MARRIAGE - Nothing Underneath)
wimmedia.com is who I usually go through because I can drive there and pick everything up. they used to be quite cheap but their prices have gone up. it's also a Christian company so it's a little weird sometimes getting harsh noise or grind tapes done at a place with a Jesus fish in their logo. I only get cassettes and cases there, I do the labels and covers at a local shop just down the road from me. used to end up costing under $100 for 50 tapes/cases/labels/covers. last job I did was closer to $150 sadly. will continue to use them out of convenience for all future releases. (RUSALKA - Blood Comes Anyway, SUBSIST, SIX BREW BANTHA - Live With Doom, THE RITA / WORKER)
USA:
I have used A to Z Audio before. nice folks. price comparable to
duplication.ca. only did tapes and cases through them. shipping to Canada was a bummer. (WINTERS IN OSAKA - Red Passage)