Tell that to the federal government.
Either way, rates go up or the purchase price goes up. So your point is?
Once interest rates get high enough, the delta will be too high to build all of it into the purchase price and shun away cash buyers. You won't see the same kind of pricing structures once interest rates climb into the 7 plus range.
The difference in the interest rate is not always equal to the cash discount. A company financing tractors (or cars or whatever) may be willing to take a smaller margin if they can sell more units. Considering the rate of return you can usually get from investments on average, I'm pretty sure Kubota could make more than the extra $600.00 they charge to finance at zero percent for $25,000+ tractors. Obviously they aren't going to lose money (if they can help it), but they will offer same/similar products at different prices to different consumers- hence the reason why there are three L series tractors nearly identical, yet for different prices. So you can actually pay "less" when financing the tractor assuming you invest lump sum you would have otherwise used to pay cash. Then there are those folks who simply don't have the cash and need to finance. They are at the mercy of the finance terms, even if rates go up.