How much is the difference between these fuel types in Your country?

In Finland the most common fuelgrades are E95 (1.449) and E98 (1.479).
(Price Euros per litre today in Kuopio city.)

As You can calculate I wont get much savings by running E95 compared to E98 so I use the E98 hoping that I�m buying a better product...

There were 2 points I was tying to get across:
- Without knock sensor + variable timing engine ignition management system, higher octane than recommended fuel will not improve the engine performance (in theory anyway) unless there is a problem with the engine
- The high octane fuel in the UK (shell, BP, maybe others also) contains additional ingredients to help the running & long term performance of the engine which can be a benefit to everyone irrespective to the first point I mentioned
In the UK we have 98~102 for high octane the price difference is about 7 pence /ltr (10 € cents?).

at 60mpg a few extra p per litre might add an extra quid to a fill up.

I'm a high milage rider, I tend to stick to the Premium fuels, more for the cleaning effects than expecting better performance per se.