You choose the asking price for the prepaid value you are transferring.
You do not have to offer a discount, but a discount can give Buyers a clear financial reason to choose your Listing. Any discount comes from the value you have already paid for — it does not reduce what the Vendor is still entitled to receive.
Why this matters
A Buyer looks at the whole opportunity, not just the amount paid to the Seller.
They will normally consider both:
what they pay you for the prepaid value; and
what they will still need to pay the Vendors.
A meaningful saving on the prepaid value can make the opportunity more attractive, while the Buyer may also benefit from saving time and effort because much of the event has already been prepared.
Do I have to sell below what I paid?
No.
You can:
offer a discount on the prepaid value;
ask to recover the full prepaid amount; or
in an unusually scarce or desirable opportunity, ask for more.
For example, a particularly hard-to-book date, venue or Vendor combination may have value of its own.
The important question is whether the overall deal still gives a Buyer a good reason to choose your Listing.
What should I consider?
When setting your asking price, look at:
how much you have already paid;
how much the Buyer will still owe the Vendors;
how attractive the date, location and included services are;
how scarce or difficult those arrangements would be to secure independently;
and whether your asking price creates a clear benefit for the Buyer.
You can always decide what recovery level makes sense for you. Buyers then decide whether the opportunity is attractive at that price.
What to do next
Set the asking price in your Listing.
If your priority is attracting more Buyer interest, consider leaving the Buyer a clear saving on the prepaid value rather than trying to recover every amount you have already paid.