If you intend to ski at Cairngorm regularly, there are loads of places you can hire in Aviemore (Ellis Brigham etc) or The Pinemarten bar opposite Glenmore Lodge.
If you’ve got your heart set on some of your own, I’d go down the 2nd hand route. I got some mint condition Head Titan 1 season old for £150 off eBay. As someone has already mentioned there are people, who like to change their skis more frequently than some of us lot change our bikes.
Jealous by the way, conditions look great at the moment. I was there over Christmas and they only had two runs and the funicular open, so went biking instead. Back up there for some ski touring in Feb, so hopefully it’ll carry on snowing.