Thats great power for that size deck. and hard to find. It must have been a special order or switched later. NOt a bad price for a hydro and foating deck, but it is 3 years old. Find out how low they will go.
I wouldn't say "way" too much, except that it's hard to value a new mower that is 3 model years old. I got a price of $4000 a couple of years ago on a 2002 44" with the weaker 15hp kohler and no e/s. So add in maybe $300 for electric start, and maybe $600 for the stronger twin cylinder engine, and that's $4900. So around 10% off that for it being a leftover sounds roughly right. Depends on how much bargain hunting you do and what your local market is. I couldn't break down the $4000 barrier with toro back then so I passed.
You can get a Gravely 48" floating deck prosteer 15hp kawi for maybe $4100 and have a similar if not superior steering system on a newer model, so that's something to compare this deal with. The power isn't nearly the same, though. But it may be fine for most use.
I owned a Toro 44" hydro for a short while and will say that unless it's the "classic" horizontal pin deck you probably won't like the traction (improperly balanced, deck seems too heavy) and the steering is a little jumpy for my tastes. I bought mine used and sold it after a few months. Worked well with a velky to weigh down the rear but spun tires a lot w/o one.