It appears that, when flying Condor, paying for extra baggage at the airport will be a lot more expensive than paying for it beforehand (online):

"All Flights to/from Zone 3
Excess Baggage Charges
€20.00 per kg
(payable at airport only)"

Source:

https://www.condor.com/eu/flight-pre...ss-baggage.jsp

By contrast, you can purchase excess-baggage "packages" in 5 kg. increments online, at a much lower cost, up to 8 hours before departure time. You obviously would need to have a good idea of the weight of the excess baggage in order to purchase a package online.