The issue would be the ability to finance. If a buyer were to buy the coach for X amount then need to put Y amount more in for tires before they hit the road it might eliminate some prospective buyers. As we all know, we live in a "how much is my payment" society and they will buy to that amount. Needing to add another $1500 +/- for tires might be more than they can handle.
If the buyer were to buy it for X amount all ready to go with no added costs to them, the increased selling amount would simply be rolled into their payment.
Assuming an extra $1500 spread over 10 years at 8% the buyer is only looking at an extra $18.20 a month.
Those $1500 tires now cost them $2,184, and the loan will last longer than the tires, but sadly most buyer won't care - as long as they can make the payment...