One root holds two senses that English splits: dear (precious to the heart) and expensive (precious to the wallet). In Hebrew they are the same word, yakar is what you treasure and what costs a lot. From this single idea radiate the loved one, the price rise, and the verb of making something cost more. Watch the price slide quietly into affection and back. Every form is verified against pealim, niqqud included.
The same root runs through the verb system. Each binyan is a voice: it bends the one idea into active, passive, causative or reciprocal. Tap to hear.
The pa'al here is stative and literary (something is dear), not an everyday verb; in daily speech the adjective yakar does that work. The pi'el is causative-intensive: to actively make a thing cost more. The passive partners pu'al and huf'al are not lexicalized for this root.
Same root letters, different noun moulds (mishkalim). The mould tells you the function: who does it, the act of doing it, or the thing produced.
Strip the prefixes, suffixes and vowels. Three consonants remain, and the meaning lives there.