My recent experience was that a used B7510 was 40% of what a new equivalent one lists for. Obviously 'used' encompasses a very wide gamut. I found an 18 year old B, with 1k hours in what seems to be very good, well-maintained condition, from an owner selling for the 'right' reason (downsizing after divorce).
If you go this route, don't be in a hurry, but be ready to make a move when the right one pops up. Good ones are not that common, and sell quickly, at least based on what I saw here in Indiana over the last year or so.
With my old B7100 still going strong at over 3k hours, I'm pretty sure this new one will do for my needs. That said, no guarantees on a used one - if you aren't willing or wanting to take the chance, just buy new and don't look back.