Actually Polish version has 4th frog worth investing into, you get about ~2x ammount of invested coupons which in fact is a really good for fast coupons in larger ammounts (comparison: SS covnoys for ingots give 5.83 coupon for ingot spent but you are limited to twice a day, so 70cp for 12ingots; spacetime bets is currently used for the same purpose with 2:1 ratio).

Regarding our version, 1st frog is decent as well, but it offers over 3 times value in items, not coupons (which in general is worse than coupons).

In all cases, its not deposit as event's description says, but its pay to get instant X reward and 6x Y during next 6 days.

Platinum is great for translating large ammount of ingots into cp. It's 2.46:1 cp:ingot ratio so its decent. Keep in mind most of people who use ingots use daily try your luck, which oscilates around 2.5:1 ratio as well. Thats a * good change :)