The big rock blocking your way in dungeons is often hiding a treasure chest, so yes it’s worth breaking if you want to open that chest. You decide if it’s worth it or not, but I’ll tell you why I think it’s worth it on the next paragraph. Many times players also wonder if the chest behind the rock is special, if somehow it has a better chance to drop valuable items. It’s safe to assume that it’s just another random chest, but then again, Cliff (the dev) is teasing us with such messages:
Now to get back to why it’s worth breaking the rock… even if they’re not special. Using a melee weapon is time consuming and using a bomb costs gold, so it doesn’t look like it’s a good trade for a chest that will probably only give you 10-30 gold (depending on dungeon) but think again:
A red devil (bomb) costs 30-50 gold, HOWEVER, you won’t have to buy it every run, because rocks show up less that you might think (once in 5-10 runs, in lower dungeons). So you’ll pay 30-50 gold every 5-10 runs, gain some back (from opening the chest) plus you get a chance at a valuable drop. Seems like a decent deal.
During events (Halloween, Easter, Xmas and others), the special items sweeten the pot, because you will get such items (like golden eggs, creepy coins so on) from almost every chest, and they’re worth much more in gold, or in utility, than one little bomb.
Same rationale can be used for chests separated by lava.