Learn Finnish: Pienen pakkauksen kilohinta on melkein kymmenkertainen. - The price per kilo of the small package is almost tenfold.

It combines the number kymmenen (ten) and the suffix -kertainen (which relates to kerta, meaning 'time' or 'instance'). Notice that the root here drops the final -en from the number, making it kymmenkertainen. While -nkertainen is the typical suffix for most numbers (like kaksinkertainen for twofold), numbers ending in -nen like kymmenen often use their shorter root form in compounds.

Why is it pienen pakkauksen instead of combining it into a single compound word?

You absolutely could use the compound word pienpakkauksen, which is very common in retail contexts! However, keeping them separate as pienen pakkauksen (using the genitive forms of pieni and pakkaus) sounds a bit more natural in everyday speech when emphasizing the size of the specific package you are looking at.

Why does kilohinta not use the genitive form, like kilon hinta?

Kilohinta (unit price per kilogram) is such a standard, established concept in Finnish that it forms a nominative compound word. If you were talking about the price of one specific, physical kilogram of something (for example, 'the price of this exact kilo of apples'), you would use the genitive phrase kilon hinta.

If I wanted to say it 'costs ten times more', could I use kymmenkertainen?