termui: only display money when non-zero

diff --git a/termui/termui.go b/termui/termui.go
index 139f09e..24f663b 100644
--- a/termui/termui.go
+++ b/termui/termui.go
@@ -364,13 +364,15 @@
 
 func (ui *TermUI) updatePrompt(thinking bool) {
 	var t string
-
 	if thinking {
 		// Emoji don't seem to work here? Messes up my terminal.
 		t = "*"
 	}
-	p := fmt.Sprintf("%s ($%0.2f/%0.2f)%s> ",
-		ui.httpURL, ui.agent.TotalUsage().TotalCostUSD, ui.agent.OriginalBudget().MaxDollars, t)
+	var money string
+	if totalCost := ui.agent.TotalUsage().TotalCostUSD; totalCost > 0 {
+		money = fmt.Sprintf("($%0.2f/%0.2f)", totalCost, ui.agent.OriginalBudget().MaxDollars)
+	}
+	p := fmt.Sprintf("%s %s%s> ", ui.httpURL, money, t)
 	ui.trm.SetPrompt(p)
 }