You owe your players 10* treasure parcels a level, but the payment terms are very flexible.
After each of the baseline 10 fights to level? Sure. All gathered up in the end boss's treasure room so they can open the door and act like a rich duck? That might leave them a little short on consumables for a bit, but that works too.
Some of them pooled together in notable caches, and others broken up into tinier pieces and spread out to be found or looted after combat since your party's looking to find and loot things after combat? Especially if your party is aggressively interested in looting the room, you can even "break up" single magic items into components they can find and put together. There are a couple other little considerations:
If you described something notable about the room, make it notable for treasure purposes, too.
There are notable things about "the room", right? Or complex of tinier rooms, or wherever it is you fought? Big central altar? Secret compartment or a pattern in the runes. Weird cutoff corner? Hidden wall. Overlooking balcony? Sounds like a nice place for a stash. Abundant plantlife? What could be in the roots?
You can and should also flavor the smidgen of treasure they find in keeping with the larger dungeon aesthetic. 4E is extremely friendly to reskins, and there's no reason "a vial of alchemist's fire" can't be a weird flower bud or a sealed heart fragment of a fire archon or a fragile portal to the Elemental Plane of Fire.
If you want to give them a challenge to overcome to get the treasure, give them a danger to avoid or a benefit to risk.
Nothing on the level of a skill challenge, really; just a single roll to find something or disarm or manipulate something small and notable. The treasure's there because it's a fair amount of treasure to have, so don't "hide it behind" a skill roll they have to pass or lose it.
Either they avoid a small amount of additional on-tier damage, or you can give them a little something extra to find. Nothing huge, just an on-tier consumable or rough cash equivalent.
Don't pull a roll out all the time; only when you feel like you can make some tension out of it. There's nothing wrong with just letting people find the treasure that's there to find, even if it's not in plain view but might be uncovered by the normal process of searching.
* Depending on your player count and other optional features like inherent bonuses, this number may change, but it will always be greater than 0.