Honda cbf 500, follow-up cost calculation?

Hello together 🙂 I was the first motorcycle to have a CBF 500 with 20,000 km, ABS, undressed for 2600 in view. The seller pointed out to me that within the next 1000km the tyres as well as the chain would have to be changed. What comes to me financially? what costs a new set of tires, the chain + installation altogether? How much can I trade down the seller due to this “minder”? (the 2600 euro are set in the sales portal without the defects as VHB.) Looking forward to your opinions! 🙂 lG