I got pretty shafted by these guys, please read full review if you want details.
First I want to mention that the tech himself, Vern, was great. Nice guy with a lot of experience and patience when answering questions about his work. My oven wasn't heating at all so I contacted Aj's. The tech took one look in the oven and immediately saw that the heating element was busted. Honestly, I messed up by not looking more closely at the oven before having someone come out because it was very clearly broken. Fair enough, he got on his phone for a bit to find the part needed and then quoted me $345 for the full repair, $200 for labor and $145 for the heating element. Knowing nothing about ovens, I agreed and paid half upfront and was to pay the second half when the actual replacement appointment was completed.
After the tech left, however, I did a bit of research. Again, I screwed up and should have done this research first - unfortunately I'm very busy and also trusted they wouldn't overcharge me, but boy was I wrong. Turns out that they are charging customers double for parts, as I could have the exact same OEM part delivered to my home tomorrow for $75. I also found out that replacing a heating element (for my oven at least) only takes a screwdriver and about 20-30 minutes of work even for a complete amateur, so their labor charge in my case would work out to about $400 per hour!
Obviously I was unhappy with this, so I called back and expressed that. They refunded about $50 of what I had already paid (down to their flat $120 diagnostic fee). After all was said and done I basically paid $120 for a tech to look at my obviously broken oven and say "yep that's broken", taking a total of ~20 minutes in and out (though for some reason he stayed parked in my driveway for about 20 minutes each before and after the appointment). Like I mentioned before, part of this is definitely my fault, but if they had more reasonable and scaling prices instead of charging $200 flat for labor and 100% upcharges for parts then I would have been fine paying them to replace this instead of doing it myself.