The Russian-Austrian negotiations have already begun. Alexander II is not a reckless man; the main reason for defaulting is a lack of funds, which does not mean he is unaware of the consequences of losing credibility.
Even if there is an intention to default, it must be done with the least possible impact, for the Tsarist Government will have to rebuild its credibility one day in the future.
The more negative the impact now, the harder it will be to make amends in the future. The Russian Empire still needs to export grain, so relations with the countries of Europe cannot be entirely ruined.
Otherwise, even if grain is sold at rock-bottom prices in the future, no one will want it. It will be tragic, as an excess grain production capacity can also lead to an economic crisis.
Relying solely on Russia's domestic market is not enough to maintain an economic cycle. The era of isolationism has ended since the Industrial Revolution began.