Well, I'm glad you found this place on the worldwide web. There is someone likely here, that's fixed whatever problem you come across.
Looks like there is a volvo and Cat dealer on sao miguel. I take it that's where any support comes from?
A island of 3,500 people may make it tough to keep a backhoe busy, but if there's no competition, that makes it easier.
Bankrupt construction companies? See- there's your sign to not buy new equipment. You don't want to be in that category.
So if you are EU- you really have all of southern europe as your shopping area for used equipment? Spain, Portugal, southern france- Italy?
$100,000 is a great budget. 30-40,000 eu would buy a pretty nice used backhoe in the U.S, If the salt air is going to eat it up, there's no reason to buy new.
What's it cost to get a backhoe from portugal or spain to the islands? $10,000- $20,000? Can they offload at your port? What's your support for fuel/ oil / supplies?
Here's the way I look at equipment in a remote environment.
Transmission and engine axles, are a wash between new and old- the new has emissions in the engine, but used engines have hours and some age on it. Any problems in these components is going to take someone expert to fix.
Where the real difference is in the "control" systems. Anything new is going to be electric joysticks, wires, and electric controlled valving- to the cylinder. Older is going to be a lever or pilot hydraulic joysticks, controlling a valve body to the cylinder. If the newer quits working, it can be the electric joystick, the wiring, the electric controlled solenoid on the valve body, or maybe the ecu if its can bus. All of which take a pretty good electric guy, and/ or the laptop to figure out why its not working. The older system, there's likely a big puddle of hydraulic oil, which is going to point you to why its not working.
So why is it electrical today instead of the older style? Because its cheaper to build a plastic joystick and run wires than the old system of hoses and levers. Its not more reliable, its not longer lasting, its cheaper for them to build.
As another "example". Monday morning- you go to start the backhoe, and nothing happens when you turn the key. A "older" machine- you need 12v to the key, 12v leaving the key, 12v at the starter from the batteries. A small jumper wire will bypass the key portion, and a hammer smack will diagnose a stuck starter solenoid.
A new machine can be any of a number of safeties in the ecu, seat belt, canbus, and all the engine systems, as well as a starter with a stuck solenoid. And bypassing 12v to the starter solenoid and a hammer smack- isn't going to get it running.
Good luck with your search! Don't get burnt out on finding the "exact" perfect machine, sometimes good enough is "good enough". If you have some used equipment you're looking at, post up links and pictures here, and there's plenty of free advice on models and years to buy, and what to avoid.