Well there must have been a price jump when they upped the engine hp from 21 to 23 and 24 to 26 on the TC series tractors this year! A MMM & FEL can add $5000 to $6000 to the cost. The tiller, depending on brand can run from about $900 to $2500 for something in the 50" size range. The problem with pricing is that it is very regional, here in N.W. Indiana I would say the price quote you got seems a bit high, but then again I've not seen new pricing on the TC23/26. (I own a TC24/MMM/FEL and a Kubota B2910TLB)
Here on TBN we do have a couple dealers in North Carolina who often have some very hot pricing. There is also Neil Messick in Pennsylvania who is a TBN member, and a New Holland & Kubota tractor dealer, I believe he delivers into Virginia.
I did price out a
B7510 about 1 year ago, the price you got on that seems high to me also. Given the choice of the
B7510 and the TC26, I would easily choose the TC26 for a 6 acre property, but I'd really want to research that price because I don't know that I'd be willing to pay that much, at least not until I shopped around a lot.
The Kubota will have a smoother running engine, IMO. They also have reportedly some of the lowest incidents of warrenty issues of any brand and are very refined. I think the Kubota is a great little machine, and a better choice for mowing because of its lighter weight. It gives up some FEL capacity, but you don't seem to indicate that is a prime concern and to be blunt, most of us don't push our little tractors to the extreme all the time. If time equaled money, then I'd want all the capacity I could get, but the practical difference is that to move a large mound of dirt from point A to point B, you will probably make 2 or 3 extra trips with the smaller tractor, so it really is not that big of a deal.
The TC26 gives you the abiltiy to pull a bigger tiller and turn a bigger mower deck. It also gives you more capacity on the FEL.