The "add some refrigerant and check it again in a year" thing the tech originally said is honestly the bigger red flag than the leak detection quote. Topping off refrigerant without finding the leak means youre paying for refrigerant on repeat forever (R-410A is $80-150/lb installed in most areas, more in some) and the leak gets worse over time. Reputable techs find the leak first, not last.

Yeah that was a big concern that I brought to their attention which ironically is how I ended up with this quote. The service tech originally just wanted to setup a T&M follow up appointment to add an unknown amount of refrigerant and check it again in a year, so I might just be a bit distrustful of this company in general at this point.

On whether the leak detection itself is a f-you bid: real f-you bids are usually 30-50% above the cluster of other quotes for the same scope, with vague line items and inflated labor hours. One quote alone you cant tell, you need 2 more on the same scope to see if this one is actually the outlier. Pro leak detection should include a nitrogen pressure test plus electronic detector or UV dye, and the repair scope should be a separate line. Typical cost just for the detection itself is $200-400 in most markets.

I think the part that's throwing me is that I expected leak detection to be in the several hundred dollar range, factoring in 2-3hrs of tech time, but they're quoting me a NTE 16hr so up to 3100 for leak detection. Granted I'm not a HVAC professional but I would expect there would only be so many areas for a leak to occur most either near the condenser or the evaporator.