When you say "inflation based monetary system", do you mean inflation targeting frameworks (where a central bank would target 2-3% inflation, for example)?
Mises typically said the polar opposite to whatever Marx said, which means that whenever Marx gave a half-trugh, Mises gave an opposite half truth. For example, Marx conflated land with capital to attack capital and Austrians conflated land with capital to defend capital. Neither side should have conflated them.