Q: When the person who enhanced is entitled to his expenses or the going-rate, how do we ascertain how much?
A: To collect his expenses, the enhancer must provide proof or swear a severe oath (holding a sefer Torah, etc.) regarding how much he expended (C.M. 375:8). Alternatively, he can request that beis din assess the expenditures, based on the materials used and minimal cost of labor, without an oath (ibid.).
Nowadays, batei din generally refrain from imposing oaths, so that — in the absence of proof — we must rely on assessing.
If the enhancer has the upper hand and is entitled to the going-rate beyond his expenses, he does not need an oath, because beis din can assess this on its own. This applies whether the going-rate is greater than the apparent expenses, so that there is no need to evaluate them, or the apparent expenses are greater, but the enhancer is willing to suffice with the going-rate to avoid swearing (Taz 375:8; Sma 375:19).
