I am not sure if I understand that correctly. Are you saying that, depending on the number of classes, a new registration costs 900-1,800-2,700€, but a renewal costs 2,120-2,120-2,120€? In that case, would it not be more prudent to take the gamble and let the TMs expire and register them anew, with only one class? (IANAL so this may be a completely idiotic idea.)
Costs for renewal of existing TM registration for 3 classes for the EU: ~2.120,- €. Deadline: 2015-08-28 Costs for new TM registration (1 class only): USA (expired): ~1.050 € China: ~1.000 € Prices contain the official fees and service fees for an agency. Prices are subject to currency fluctuation changes as the WIPO official fees have to be paid in Swiss francs.