This is a question that can't get a definitive answer, as design decisions, especially in such minor areas are not driven by singular logic - or logic at all.
First of all, in 1983 noone would have used a 8080 anymore. If at all, it would have been an 8085 (*1).
Secondly, by 1983 the price difference was marginal at best - especially when considering that it is meant as a home built computer where the builder acquires the parts - both priced below 4 USD. So why not use the better CPU (*2)?
The same is true for the RAM. DRAM only gets less expensive for larger sizes. By late 1983, 2 KiB 6116 were about 4 USD apiece, while a 16 KiBit 4116 cost 1.50 USD or 12 USD for a set. While the prices for sure were different in Yugoslavia, the general ratio should have been quite similar. The Galaksija was meant to run with 2 KiB RAM as a standard (minimum) configuration - offering two more RAM location to expand to whopping 6 KiB (*3).
More importantly, DRAM needs, as mentioned, support circuitry for address multiplexing and refresh. So while the refresh part is simplified on the Z80, the multiplexer is still needed (*4) - plus a satisfying clock source to do so. Thus DRAM increases complexity of a design. Not exactly a good thing when targeting a self builder hobbyist market (*5).
Last but definitively not least, the Galaksija was supposed to use a single sided PCB. Each and every intersection of traces thus needs soldering a wire to bridge either. A lower chip count will in next to all cases result in less wires and less intersection, thus making the job of soldering way less frustrating.
*1 - Single 5V supply is a definitive plus for any design.
*2 - At least as assumed by the general public.
*3 - Keep in mind, it uses character based graphics, so no need for large screen buffers, 512 Bytes is all that is needed. A Spectrum in contrast needs already more than 6 KiB for the display file alone.
*4 - Now, if Zilog had this as well build in, it would have made a killer feature.
*5 - For the implied question, why next to all mass produced machines use DRAM, size is the most obvious answer. Eight 4164 give a full 64 KiB (and 41464 even reduce it to two). At that size it's way cheaper than SRAM. Sheer volume and factory production vs home build also changes the rules.