What makes a massive difference is if you keep taking it back to the main dealer, as many (most?) owners of the latest brands do. That will double your costs, easily, treble if N-reg.
Why treble with N Reg?
Were you not an owner of a piston PA46, Jason?
If so, the original owner may be interested to know more, because an old one can be purchased within his budget.
Yes, I owned it from about 600-1000 hours. no meaningful work had taken place on the engine before I bought it and I had a very thorough pre-buy in the US. One turbo needed some work which was quite cheap (couple of hundred USD) and after my purchase I did very regular oil changes, flew mostly LOP and the engine ran really well. Passed its pre-buy here fine. It is a highly stressed engine but I also think its longevity depends on how you fly with it (in particular descents from FL2xx). It is the sort of plane you need to get a specialist to do maintenance on, and that doesn’t necessarily mean a Piper Maintenance shop.
I doubt you will find massive differences if you compare like for like e.g. when it comes to maintenance, same airframe condition. GA v. GA isn’t like say Audi v. Kia.
This, of course, is true only with equivalent aircraft systems. Most fixed gears need less attention than retractable gears (except perhaps when you compare a Morane gear to a manual M20 gear or a RF5 retraction system). Any TKS not installed does not need any maintenance and so forth. On the cheap end, it might even be feasible to buy two airframes, one for spare. Then it’s possible to keep flying on a relatively tight budget. Especially if you use ELA1 privileges and are able (and willing) to do much by yourself. Or, if you have real exotic aircraft, you better have a good rapport with a parts manufacturer. But this is seldom for the usual 100+k€ IFR Tourer, I suppose.
If a US import is an option, I think a closer look into the Bellanca Vikings won’t hurt. They deliver very good performance on a low purchase budget, are fast and have a reportedly nice handling qualities. I haven’t seen one recently asking more than 70k€, even with two RayJays – or without, if you please. They aren’t exactly this millenniums airframes, but are more efficient than the SR22. Just the tank is a bit small with just 60 usg, delivering around 500-600 MN range.
Why treble with N Reg?
Because N-reg gives you lower cost options for maintenance – Part 91 and getting an A&P / A&P/IA to do it freelance i.e. not using a company. There are ways to do it on an EASA-reg (G-reg, anyway) but they are harder to organise.
I’d say that, of the ~150kt retractables, a TB20, Commander, maybe the Bonanza, will do grass well, with the obvious proviso that the aircraft will get dirty and if you don’t keep the gear clean and lubed it will eventually fill up with crap and eventually give you trouble. The other rectactables don’t seem to do grass as well, due to various issues e.g. prop clearance.
This must be why you don’t find any Cessna 210 and 182 RG in Africa / Australia / South America etc. doing back country missions on grass, dirt and gravel strips and so many TB20 
The OP was only interested in low-wing.
If you can get yourself to EGKA, I’d happily take you up in my TB20GT. If not going on a trip, I fly once a week just for currency, locally
Peter, thanks for your generous offer, when we get a break in the weather I will fly down to Shoreham and take you up on that offer if that’s ok.
As an N reg plane seems easier to maintain isn’t it more difficult for the buyer to assess the value or the quality of the past maintenance?
My Bonanza loves grass.it has almost Tundra tires.. 
my previous mooney hated it. Why, well prop clearance and potential incontinence from the wet wing tanks if you do it often!
My Bonanza loves grass.it has almost Tundra tires.. my previous mooney hated it. Why, well prop clearance and potential incontinence from the wet wing tanks if you do it often!
Yes prop strikes are probably more common in Mooneys than comparable planes because of the geometry (nose wheel is a long way back from the prop arc)….the static clearance is actually quite good….most prop strikes occur on Tarmac due to botched landings…. But I agree Mooneys are not made for rough strip operation…it is actually the lower gear doors that are likely to be damaged (only about 4" clearance)…if operating regularly from unimproved strips these doors can be removed (without any approval since the POH allows it)…this will cost a couple of knots in cruise… I have operated on grass several times (carefully) without undue concern
