I have at least two characters (and maybe a third) that cannot buy the Traveller's Bundle in the store. Why? Because they picked up an extra milestone skill somewhere along the way. The bundle includes Milestone II-VI as well as Hurried Traveller and because the first one in the bundle is a duplicate, the characters are ineligible to purchase it. I really wish they would design these types of things as a non-gated items. The will, vitality, et al boosts are also like that. Instead of doing a +1 milestone unless count<X, they gate them on Tome I, Tome II, Milestone I, Milestone II, etc.
That's actually a decent chunk of TP they're leaving on the table, because I can't buy the bundle and don't want to spend the extra 400ish TP on buying them separately.