Yes, a complete set on cover is worth more than a partial set or individual stamps on cover, but this is a relative value. Modern Indonesian stamps do not have much commercial value, just like modern stamps from most every other country. First Day Covers such as yours sell on
ebay for anywhere between $1 and $7 depending on whether there is a collector who wants that particular one for their collection. It also depends on the condition and if it is anything other than perfect as the day it was first made then the value drops sharply. You should go on
ebay and study the selling prices for a few weeks to get a good idea of prices. Be sure to look only at completed auctions where the item actually sold. Those will show up with
GREEN font. You should also pay attention to how many items do not sell. This is for two reasons - first, there are very few collectors interested in buying modern Indonesian stamps, and second, most sellers put starting prices that are far above what prices those few people are willing to pay. The more valuable stamps, covers, and stampless covers from Indonesia are the very old ones. In general, the most valuable are the stampless ones from the 1800s and earlier, though there are some from the early 1900s that can be valuable as well.