If you, as a fan got extra tracks, new songs then it’s all good.
Record companies would sell in records (mainly CD singles then) before release and depending on their financial clout would off deals like 1 for 1, essentially buy one get one free to record shops. So if you buy say Bjork - It’s Oh So Quiet for a cost price of £2:50 you can then sell it for £1:99 because the free copy will see the profit - £2:50 outlay, £3:98 return when both copies are sold.
So the key here is the record shop worker (buyer from the record companies) having and eye / ear for a Hit and buying what they predict they will sell in advance for the records whole Chart duration. So on a big hit single, before it is released buy say 100, get 100 free of that Bjork song. The reason for this is when the record is established, say after 1 week and it’s in the Top 10 the deal is removed by the record company. So one copy is now £2:50 to the record shop so they can’t sell it at £1:99 anymore.