You'll see this is false and deceptive advertising.
To complain, you would need to contact eBay customer support, click on "Help & contact" or "Contact us" at the top or bottom of most pages.
First, read the terms and conditiond for the voucher carefully. In particuar, how is the "total value" defined - for example, does it exclude the buyer protection fee, if applicable? Also check the exact time limit of the offer.
Buyers who ask questions here about vouchers often find that they have overlooked somethng in the t&c.