Fuck it, having worked briefly with farmers when I was younger, I'll play devil's advocate here:
1) Farmers know damned well that companies like John Deere sell their hardware at cost (or even a loss), with the intention of making their money in servicing the vehicles.
2) Farmers will howl like dogs if John Deere says "Okay, we'll sell you models that you can fix yourself. But they'll cost twice as much to buy."
And if you hadn't yet deduced it from the previous two points:
3) Farmers are a notorious bunch of whiny cheapskates who live to complain about EVERYTHING and will go to any length (legal or otherwise) to save a penny. Seriously, asking a farmer about his farm is like asking an old person about their health--expect to hear nothing but complaints, how much they're suffering, how they need this and that, woe is me, etc. And they will do ANYTHING to make even an extra dime, including hiring illegals, buying seed they know damned well is illegal, cutting corners on sanitation requirements, trying to cheat their workers and work them off the clock, lying to the government about their crop yields to get higher insurance or fallow payouts, etc., etc., etc.
In other words, farmers want their cake and to eat it too. They want all the latest developments in the technology, and they want it to be repairable by third parties--but they also want it to still be as cheap as it is now (at the price that's based on a maintenance subsidy).
And that's me playing devil's advocate for today and risking the karma hit from those of you who've never had to deal with farmers before.
John Deere should respond. "Dear farmers: We can sell it to you cheap or we can sell it to you repairable. Pick any one."