How to change a cell to reflect an amount in another cell with numerous possible values

Hello,

This is my first post so apologies if it's not in the correct thread. I'm fairly new to excel.

I'm looking for a specific formula (not a calculation).

I have specific prices for items in my shop which have discounted RRP prices. There is no calculation to work out the discount I want to offer on each RRP but I already have set prices for each RRP. Here's an example;

RRP Selling Price
$24.99 $18.50
$30.00 $23.84
$75.00 $59.97

My selling prices never change (and they are just set prices so there's no formula to work them out) but I have large volumes of stock so it's a pain manually changing each selling price to reflect the RRP.

I want a formula which says something along the lines of 'if a1 =$24.99 then b1=$18.50 or if a1=$30.00 then b1=$23.84 and so on'. I realise this would be a long formula as there are about 50 different RRPs but think this is the only way I could do it.

Can anyone please help me with this?