Let's say that you can catch a mon per minute downtown and you sometimes get first throw, sometimes great/excellent throw and always curve, you could probably make a base of 150xp per mon. Multiply by 4 for event and lucky egg, that is 600xp per mon times 30 minutes, which would net you 18000xp. Then add some egg hatches and you should easily clear 20k. Still nothing when a lucky egg mass evolve for 30 minutes during this event should easily net you 150k.
My personal favoured method is doing a lucky egg mass evolve, while catching mon with my go plus at the same time and walking at a frantic speed hatching collected 10k eggs. I have been doing that every saturday when I have my 7 day bonuses. Usually nets me something like 100k.