Lucky you, Karen! And useful info about the going price. Once upon a time, long ago ('99), on my First trip to Nafplio, the local travel agencies offered a 1-day tour of Mycenae & Epidaurus ... I can't remember if it included a licensed guide, it must have, because I remember standing around the circle graves while someone explained. There was lunch in between (which each paid for). Howevver, it was not expensive, and VERY useful... since local bus schedules are not set up so that one can do both in a day ... typically there is a bus to Mycenae at 9 am or so, th en back at 1pm ... but then you cannot get a bus to Epidaurus in the afternoon (local busses are mainly set up for locals, to get them to work & back).
Alas, that day appears to be gone. Each time I'm in Nafplio, I stop in at agencies and the answer is the same: when a (small) cruise ship stops in Nafplio (infrequently) those on board have their own licensed guide & tour... and many people also come from Athens on a 1-2 day bus tour, which has its own guide. Thus the agencies say, not enough demand to offer a regular tour. Personally, I think if it were marked smartly there could be a regular demnd for at least 2-3 per week, judging from the constant plea by independent travelers for this service. IMHO, the local govt's lack of interest in tourism services is the root cause.
Therefore Kardell, aimed with knowledge of the price, perhaps u could write your hotelier & they might fix you up with another hotel guest!!! Good luck!