Risto I think you missed the point. Botnets have an order-of-magnitude or more lower costs, thus this lower cost basis means they can sell at lower prices, thus they drive the price of the coin down if they are too much of the float (which I theorize could impact the exponential share of the distribution and growth curve).
While the debasement rates are high, the price of the coin is modulated significantly by the cost of mining.
Thus for two reasons botnets are not a problem in the long-term, but they can destroyhurt a coin early on (when the long-term growth curve is being established and perhaps set in stone).
1. The difficulty eventually rises such that either the demand for botnets drives their prices up to parity with rented hardware or botnets fade as a significant % of the hashrate.
2. Debasement rates slow so the price of the coin is less modulated by the cost of mining.
I think you can also add
3. Because of the rising difficulty, an increasing fraction of the people who want to acquire XMR and were mining so far to that purpose now will buy instead.
So, the selling pressure created by botnets is one thing. On the other side of the coin (pun intended), also buying pressure should build up. Economically, the only reason that these two effects do not perfectly neutralize each other is that they do not happen at the same time.
That's how I see it, from an economical perspective at least. Hard to figure out the psychological effects, though.