Is $748 to recharge R410A refrigerant a fair price?

I'm a DIY homeowner but HVAC is outside my expertise. I had my yearly preventative maintenance check, and the technician said there's likely a refrigerant leak based on low readings (shown in the photo). The AC unit is 5 years old, but the lines and evaporator coil were not replaced by the previous owner when the unit was installed. The same company has done maintenance for the last two years but didn't document gauge readings or clean the outside unit according to the current tech. They replaced my capacitor last year for $450, which I felt was overpriced. My furnace was installed 2 months ago, and the technician warned about potential flooding from the evaporator coil if there's no failsafe, but my drip pan actually has a float switch (which he didn't mention). I paid $130 for a tune-up two years ago and am upset cleaning wasn't included. I'm considering adding a water sensor as an extra failsafe and plan to get a second opinion on the refrigerant charge cost and leak test.