Because consumers can only see online terms and conditions, which are hosted on respective business websites.
They can change at their will.
I purchased a sofa from a business which sells ex demo, ex rental, discontinued items, excess orders, seconds furniture.
This business has a website and warehouse/office etc.
On their terms and conditions on their website on sale day it was written (deposits of $50 per item purchased. Items over $1000 requires $100 deposit.Your deposit secures the item and it's non refundable).
On sale day I choose an item with price tag of $1000, the sales representative said to pay $100 deposit.
I said Items over $1000 requires $100 deposit, other items require only $50 deposit.
I didn't have internet access to show this sales representative, so I just paid $100 deposit.
After coming home I checked terms and condition and ask for return of the extra deposit of $50 I paid.
Within minutes, they change the terms to "Once you have selected an item, a $50, non refundable deposit per item (under $1000, $100 for items over $1000) is required to secure your purchase, and refuse to refund extra deposit I paid.
I don't get it? You paid twice the deposit you had to so would like half of it back but the store duped you even though it's a deposit and you still need to clear the balance? Cool story though.
edit: I see you've edited but I'm sticking to my original. Surely they subtract the deposit payment from the total … what's the real problem here? Are they ripping you off or are you that bored you want to fight for 50 bucks that you shouldn't have had to pay immediately but certainly needed to pay at some point down the track?