What FSR said...so many things can go wrong...and it's not always the fault of the inseminator.
Heifers not in good body condition... or not cycling...mineral deficiencies...bad semen(it happens...have experienced it)...poor heat detection (that's where the bull excels!)...insemination too early/late...ambient temps too high resulting in early embryonic death...malfunctioning thaw unit, etc.
You didn't say what you paid for semen, if you did TAI or bred on observed heats; but if you used 'high-dollar' semen, you could get on up toward that $1600 figure pretty quickly...
I rarely spend more than $25/unit... have gone as high as $40... wife paid $135/unit for a particular bull she really wanted to use (got a deal at an auction, as it usually went for $200/unit); but I've seen some old dead bulls in high demand go for upwards of $650/unit...at that price, I'd only be using that for a superovulated flush to (hopefully) produce multiple embryos for ET implantation.
I keep seeing posts about folks having their veterinarian doing AI, or recommending 'have your vet do it' . Granted, I've spent most of my career in the Southeastern US, but I've never personally known another vet who has the time or inclination to be doing AI for the public. Sure, maybe some of the folks who specialize in repro/embryo transfer... but not your typical large animal or mixed practitioner. But maybe they do, elsewhere.
I know I never would have had time to be running all over the county to breed a cow here and there - on time - when I had medical cases to deal with. I had enough on my plate trying to satisfy clients with medical/surgical issues, much less having a disgruntled client over low conception rates - that might or might not have been related to anything I had control over.
I'd lay money that an experienced AI tech is gonna do a better job than most veterinarians, with regard to semen placement... I 'know how' to do it - but I've never passed an insemination gun in my life; I've palpated plenty of cows/heifers in my day... I'm still in awe of anyone who can thread that thing through a heifer's cervix...
My vet(wife) does the AI here - and her conception rates typically run ~85%... but the first year she inseminated our cows, AI conception rates were around 30% - some of that low rate was on her, but some was related to condition of the cows at that time. Practice & experience has improved her success rate substantially, but making sure the cattle are in good body condition and cycling properly - and inseminated at the proper time - is equally as important as competence of the inseminator.
