  We revisit the wall-crossing behaviour of solutions to the Thermodynamic
Bethe Ansatz type equations arising in a class of three-dimensional field
theories, expressed as sums of "instanton corrections". We explain how to
attach to an instanton correction at a critical value a set of (combinatorial
types of) tropical curves in R^2 of fixed degree, which determines its jump to
leading order. We show that a weighted sum over all such curves is in fact a
tropical count. This goes through to the q-deformed setting. Our construction
can be regarded as a formal mirror symmetric statement in the framework
proposed by Gaiotto, Moore and Neitzke.
