Is Audio Research PH3 phono the best for today's price?

It depends on what you want. I had a PH3 loved it. Being tube based (Not all tube) it had some noise, but it was very minimal. Great detail, if you find a used PH3SE for $400 - $500 more, it's worth the upgrade. I now have an ARC Ref Phono, it's noiser because it's an all unit, but it's been upgraded by Nick Gowan and I use NOS tubes so it's very quiet and has great dynamics. ALL ARC tube gear benefits greatly from getting different tubes.

It seems to me that PH3 needs a freequent retubing like a baby needs its diaper changed. You change the tubes every 1.5 years -- it feels better and sounds more open and faster.
Any thoughts?

With good tubes, probably 4 to 5 yeras.

Bingo! What is the best way to get high quality tubes? Their retail price is usually $100 each. I can see that some of them go off ebay for $25-30 a piece. Are these tubes fake? In fact I do not know how to distinguish real ones.

You can get great tubes for $50 - $60 each from eiher Upscale Audio or Vintage Tube. I use Mullards. I would only buy tubes from a respected dealer or with some sort of documentation.