relative price of a transistor and a capacitor
The question isn't necessarily about the relative cost of each transistor versus each capacitor. Once the masks are made for manufacturing the silicon chips, a chip made purely of transistors wouldn't cost any more than a chip made of purely capacitors (Excepting the number of steps in the manufacturing process, which a mixed chip would need all steps anyway).

The difference comes in the real estate on the silicon. The simplest way to store a single bit in SRAM (Using purely transistors) requires 6 transistors, and is made this way:  

Image pulled from the SRAM wikipedia page.

Alternatively, we can use a DRAM cell. As you mentioned, DRAM uses one transistor and one capacitor, which means we can fit many more of these two-component storage cells onto a single chip than the six-component storage cells. DRAM is cheaper because it can be made significantly more dense than SRAM, not because of the relative cost of the transistors and capacitors on the silicon chip.