He's your friend. Give him a fair deal.
FW 4.5 3DS Xl's sell in Canada for about $220-$240 (canadian).. the normal 3DS Xl's are about $180 ($40-$60 difference). A used 3DS can be found as low as $130.. I would say a 4.5 or lower 3DS should be anywhere from $170 on low side and $190 on the higher side. If you go in the middle and offer $180, I think that would be fair. Looks like you live in england so in pounds $180 CAN would be like 100 British pounds sterling. Can anyone else give an idea of how much a normal 3DS <4.5 are worth?
In Canada here, I found a 1.1 3DS for $100 with OoT3D on Kijiji. Don't limit yourself to pawn shops and whatnot, check Kijiji and Craigslist. If they're innocently posting it, like, say, their kids used it, or they got it a long time ago but haven't used it, send them a message and get them to check the firmware, since it's very easy to do. You might score a good deal doing it that way. Just don't mention that it's exploitable in any way, perhaps say that you're looking for the oldest firmware you can find for collector's reasons or something, or else they may jack the price on you unexpectedly.
I was able to get a new 4.4 XL at a really busy Futureshop. They only had two left and the other one had a similar 2012 serial number. I'm pretty lucky that they had any old consoles left.Well it really depends on where you live and how lucky you are... I got my 3DS XL from kijiji in January 2014 for $200 (sealed mario kart bundle unit with warranty). It took me about 2 months of looking around on kijiji and I even made a post for people to contact me if they had units under 4.5 but no reply's. At a point someone did message me and said it was 4.5 but when I went to pick it up and checked it was 6.x... I must have messaged over 15 people that had ads and they all had updated to the newest firmware. I was lucky to later find mine for $200 cash since they are $199 plus tax new and wont be < 4.5.