The event costs 225 gold per run which means you break even at a roll of 15 or higher (assuming you value a gem at 20 gold, a rare at 50 and a common at 5):
In contrast, the normal Sharpstone Keep challenges costs 50 with a break even with a 6 roll or higher:
You have about a 66% chance to roll 15 or above with 3 dice and 98% to roll above 6 with 3 dice.
What does this mean? If you have a large amount of gold but need gems, you should do this challenge. But if you are short on gold, you may want to consider skipping it, especially if you can’t beat all 3 bosses. The chances of profiting drop to 51% with 2 dice and 30% with a single dice.
The event team usually sets the entry price of an event at the base price or 150% of the base challenge price in gold or the equivalent in gems, with the appropriate rewards. This is the first time I’ve seen a challenge be set at 450% of the base fee. However, I understand the rationale. Gems are a premium currency and since the latest economy updates, Ludia has been reluctant to offer gem events, especially non-VIP events. It seems that they revised their position, but would rather disincentivize players by decreasing the return per run. I suspect that this is in response to some strong criticism regarding the availability of gem events both on this forum and other social media platforms.
For me personally, I like that they give the players an option to effectively exchange gold for gems, even if it isn’t at as good a rate as before. However, that’s only because I have accumulated a tremendous amount of gold. It is a pretty raw deal for new players.
Notably, the event team has been playing around with various elements of challenge events. The 450% entry fee is the latest manifestation of this trend. Previously, I took note of reduced rewards table for a VIP event here: [Intentional] VIP only Calliope Moment of Glory - Heartcoil Deeps Reduced Rewards Table (equivalent to Frostsilver Mines)
At the end of the day, I’d rather overpay an easy event to access a gold to gem exchange, than to play a hard Dungeon to get crappy rewards.
Nevertheless, remain vigilant on how aspects of challenge events change going forward. I think we are going to see a lot more tweaks to costs and rewards in the future.