I have seen good annuals, and bad. First one I paid for was nothing more than a looking over, rate was $2k. No compression check, no wheel bearing pack, nothing. In the first 6 months after purchase I replaced the tailwheel, and one fuel bladder. Annual number two was $800 done by a "friend", he basically did a compression, and looked at a couple of items, but said the 50 psi on #5 cylinder was ok, he didn't borescope it. I was helping, but didn't know what I didn't know at the time. 3rd annual was done at my employers hangar, he has 4 full time pilots and 2 full time mechanics. That annual was free for labor. We found old damage in the horizontal, 4 ribs were detached on one side. We found #5 cylinder with burned valve, 2 sheared rivets on the right gear box, cracked cross over tube, incorrect hardware in a few places, cracks in the airbox. That annual took 6 weeks. Annual #4 was me with supervision of the local shop, even with the extensive annual the year before, I still found several small items, like worn out throttle and prop rod ends, worn out carb heat shaft and bearings, carb to Y pipe bolts not tight, spark plugs pretty much worn out, bad / incorrect prop cable, and a cracked #1 cylinder. Annual #5 was again me with supervision of the local shop, all I needed that year was a new throttle cable.
Usually you get what you pay for, but if you find someone that really looks the plane over and goes through everything, pay what it costs, its worth it.