view(Purchase): minor fixes.

tienda_ilusion/don_confiao/frontend/don-confiao/src/components/Purchase.vue

@@ -59,6 +59,7 @@
                 label="Precio"
                 type="number"
                 :rules="[rules.required]"
+                prefix="$"
                 required
                 readonly
               ></v-text-field>
@@ -74,9 +75,12 @@
             </v-col>
             <v-col>
               <v-text-field
+                type="number"
                 :value="calculateSubtotal(line)"
                 label="Subtotal"
+                prefix="$"
                 readonly
+                disable
               ></v-text-field>
             </v-col>
             <v-col>
@@ -93,6 +97,7 @@
         <v-text-field
           :value="calculateTotal"
           label="Total"
+          prefix="$"
           readonly
         ></v-text-field>
         <v-btn @click="submit" color="green">Comprar</v-btn>