In fact you are not getting the full idea behind that concept.
You can upgrade from a interior to any other category (upto YC3) each upgrade step (was in my case 750EUR for 2 people).
Up to you ofcourse to do the calculations..
eg.
1 week cruise in YC1 Med July for 2 people (BCN depature) = 4798 EUR TOTAL DUE
30% discount is = 1439 EUR discount -> 3359 EUR TOTAL DUE
Free Interiour -> Ocean -> B1 -> B3 -> YC1 = 4*750 EUR = 3000 EUR TOTAL DUE
So in fact the total FREE interior + upgrades is 359 EUR cheaper compared to the 30% discount.
As far as I remember 30% voucher is assigned at 1250 points, free interior at 10000 points.
Hope this helps 🙂
