Toyota Repair: 2001 Toyota Sequoia, A/C not blowing as cold as it used to, toyota sequoia, informative place

Question
Hello Ted
Nice Informative place you have here, I hope you can help
My Sequoia seems to not be blowing as cold as it used to, I took it to a local shop here in Las Vegas with a big sign out front that said "FREE A/C CHECK" so I pulled in and after about 20 mins the mechanic came back to tell me that my system has a leak because it was very low on fluid, he said it was at about half pf what it should be, He would not tell me what the pressure was even after I asked 3 different times, I found that a bit odd, So then the mechanic escorted me to the office to talk to the guy behind the desk, He was a bit busy doing about 3 other things when he looked over at me with a very concerned look and said " Hey buddy its gonna be $500-$600 because I had a leaky system and it would be like a 4-5 hour job.
I gladly thanked him and told him I would discuss it with my wife and call them later, So on the way home I stopped at my local AutoZone and bought a R134 recharge kit for $50 and some cans of R134 with stop leak, whew!! sorry I talk too much
I arrived at my house and hooked up the gauge to the A/C system and it gave me a reading of 30psi, this is where my question is , I am going to this myself but have had no luck finding out what was the MAX PSI I should fill it too is
p.s. the mechanic told me that a good working AC system will no leak even after 10 years your pressure in the system should be the same, so thats how he knew that my system was leaking. and thats why they would have to do a complete system reseal, and all he did was hook the AC pressure machine to my car  

Answer
You did the right thing by getting out of that shop, anytime a shop recommends any repairs you should get a full explanation of what needs to be done and what parts need to be replaced up front. Not"hey buddy you got a leak and it'll cost $600 bucks" very unprofessional. The pressure on the low side should be around 30 psi and the high side reading should be about 150psi with the compressor running. Let me warn you up front that these year model seqouias had some known a/c compressor issues and toyota has issued several service bulletins on how to go about repairing this problem which may involve replacing most of the a/c components because of compressor failure which will distribute metal particles throughout the entire system, I'm not saying this is the case here but it is something you should know, I would recommend having the toyota dealer check it, pay the diagnostic fee and have them make a recommended procedure for repair. If you were able to add about one pound of freon and the compressor turns on and the system gets cold it is probably just a small leak somewhere but if the compressor makes a lot of noise and eventually stops there is a major problem.