Of course there is a cost to DL. It may not be an outright cash expenditure, but there is a branding and goodwill issue with other customers who are competing for a limited number of perks. It goes without saying that none of this matters in the context of any one customer. But, if DL effectively expands the universe of qualifications for a given status level (that is what a "soft landing" is), it is then accused of a devaluation.

I would not suggest buying a lot of non-refundable tickets. Nobody here can say whether that motivates DL to see you as a candidate for a "soft landing" or whether DL identifies such a person as already loyal and thus not requiring a sweetener.