Getting ripped off here, help

There was an album I wanted to buy in iTunes that is $16.99, I was short a few cents though so I started buying some songs in the album separately. When the price knocked down to about $3.00 I decided to buy one more, as I knew to buy the rest of the album I would have to pay at least a few more cents... BUT, when I did so the album went back to the full price! Each song separately is $2.19, and I still have 4 more songs to buy now which adds up to $8.76 and apparently I have to pay $16.99 to buy the full album but really all that I would need to pay is $8.76 after this dilemma, but it shouldn't even be that, it should only be a few more cents, only about a $1.00. I really need this fixed because I don't have much money to begin with as I don't even have a part time job yet. I'm in high school, I shouldn't have to put up with this. Please help, I shouldn't have to pay another $8.76.