diff --git a/pinaxcon/templatetags/nbpy_tags.py b/pinaxcon/templatetags/nbpy_tags.py
index 6c3142f777786a2d475561728467b79b39122548..d36055572c1ba9586928bd034607811cda4fffb4 100644
--- a/pinaxcon/templatetags/nbpy_tags.py
+++ b/pinaxcon/templatetags/nbpy_tags.py
@@ -1,4 +1,4 @@
-from registrasion.models import commerce
+from registrasion.models import commerce, inventory
 from registrasion.controllers.category import CategoryController
 from registrasion.controllers.item import ItemController
 from registrasion.templatetags import registrasion_tags
@@ -14,6 +14,9 @@ register = template.Library()
 CENTS_QUANT = Decimal('.01')
 VAT_RATE = str(settings.INVOICE_VAT_RATE * 100).rstrip('.0') + '%'
 
+def nonvat_price(product):
+    return product.price * (1 - settings.INVOICE_VAT_RATE)
+
 @register.simple_tag
 def vat_amount(invoice):
     return (invoice.value * settings.INVOICE_VAT_RATE).quantize(CENTS_QUANT)
@@ -31,28 +34,13 @@ def donation_income(context, invoice):
 
     '''
 
-    # 15% (FSA) goes to Conservancy; 85% is real goods
-
-    fsa_rate = Decimal("0.85")
-    rbi_full_ticket = Decimal("68.00")
-    rbi_early_bird_discount = Decimal("-21.35")
-    rbi = []
-
-    for line in invoice.lineitem_set.all():
-        if line.product.category.name == "Ticket":
-            if line.product.name.startswith("Unaffiliated Individual"):
-                # Includes full price & discounts
-                rbi.append(line.total_price * fsa_rate)
-            else:
-                if line.total_price > 0:
-                    rbi.append(rbi_full_ticket)
-                elif line.total_price < 0:
-                    rbi.append(rbi_early_bird_discount)
-        elif line.product.category.name == "T-Shirt":
-            rbi.append(line.total_price * fsa_rate)
-
-    donation = max(Decimal('0'), (invoice.value - sum(rbi)))
-    return donation.quantize(CENTS_QUANT)
+    tickets = inventory.Product.objects.filter(category__id=settings.TICKET_PRODUCT_CATEGORY)
+    cheapest_ticket = tickets.order_by('price').first()
+    ticket_rbi = nonvat_price(cheapest_ticket)
+    return sum(
+        (nonvat_price(ticket) - ticket_rbi
+         for ticket in invoice.lineitem_set.filter(product__in=tickets)),
+        Decimal(0)).quantize(CENTS_QUANT)
 
 
 # TODO: include van/de/van der/de la/etc etc etc