The last mk6 transit was made 10 years ago and I guess he got a NEWER van to replace that which would be hard not to improve on what he had.
Most of the mk6's wouldn't pull the skin of rice pudding and you can hear them 3 streets away.Very few were tdci most being TDDI.
You then have to look at what experience someone has driving which models.someone describing a mk7 85 ps would give a very different account to someone that has drove 130/140 models and that's why they command much more money.
After all I wouldn't want a 85ps lawn mower never mind a van that's intended for pulling weight.
Minimum you want 110 but even that (for me) is too little and not only do you have the power issue but the 130's and 140's do more to the gallon.The 130's and 140's will return easy 35's and on a run mid 40's or more.
You also have to consider many vans are just heaps of crap,like I said,finding a good one is near impossible but everyone has different views on 'good'.
The transit drives better,is better equipped and has more room than the vivaro vans which are very limited in the sizes they come in and most low powered.
And don't forget the gearbox failures that are prominent with the reno and vivaro vans.Do a google search and there is pages of pages of them failing and as there are few good second hand ones,the repair is expensive.
I personally would forget merc or VW at 3 grand,there wouldn't be any id want to own.
As for getting a good van from Auction at 3 grand....Good luck with that and VAT will be payable.