The team just signed Vardy through 2019. So far this season we have seen them add not sell. We'll have to see if they monetize Mahrez or pay him. I bet they pay him.
Besides that they don't really have anyone that other teams want. But they have a coach they play hard for. They defend and they counter like lightening right down route 1.
Leicester probably should be a mid table team last year and this and we are just seeing variance. But their chances in UCL are just as good (meaning not) as any of the other mediocre EPL teams at the top, and it's way more fun to have them than any of the others.
Another factor which has been talked about on television is that Leicester is only playing Premier League matches. The other top clubs have domestic and European tournaments still.