Rather than keeping track of individual coins and valuable, objects used for purchasing is wrapped into a wealth stat. Buying things takes a wealth test, decreasing the value with failures, while adding to wealth can (with successes) increase. Let's use size to denote wealth, i.e. the cheapest items might take tiny (S1) wealth, (S3) wealth might be middle-class purchases, up to (S9) mythical wealth being virtually unlimited resources.