Hi, I just did a statistical analysis of the droprate of Frigid Frostling and Lumpy combined. According to wowhead(the count, not the rounded percentage) the droprate of Lumpy is 2.94%, and Frigid Frostling is 3.59%. Out of these two I would say the droprate of Lumpy(2.94%) is more accurate, since its a bigger sample size(83401 compared to 16108). Funny how the sample size is bigger on a pet that has been available shorter. It's the difference of summer/winter activity that is to blame, of course, and especially the holiday boom of players. But I digress, sorry.
Why would I want to combine these two droprates? Simple really, they are both from a world event, and are only available 15 days a year. Logically there is no reason why Blizzard would differentiate between the two droprates.
The combined droprate is 3032 in 99509, or 3.04696%. I think its safe to say its programmed to have a 3% droprate.
In the spirit of fair trading 1:1, it would be safe to trade Frigid Frostling for Lumpy, or the other way around, if it hadn't been for one thing changing their value. The time of the year. These pets have highest value when it has been 5.75 months since the even ended, and when its 5.75 months until the event starts. Comparably Lumpy would have highest value 25th of June(26th if its leapyear), and Frigid Frostling would have the highest value 6th of January. You may argue that the value rises the very second the event ends since they are no longer available, but this is not true since it will be a fair amount available at the auctionhouse still. And you may also argue the value just rises the longer it has been since the event because the item becomes rarer and rarer, but this is not the case because people look in their calendar and think; "oh, I can wait, its not that long until the event". Supply and demand in perfect harmony.
I won't even try to value these pets in gold, but it is possible to put a relative value on them based on droprate and availability.
Statisticly, if you do the quest each day on one character, you will have a ~37% chance of getting this pet. If you do it each day on two characters, you have a ~60% chance of getting it. 3 chars ~= 75% chance. 4 chars ~= 84% chance. Even if you do it on 7 chars each day, there is still a 4% chance you won't get this pet..
But hey, lets be optimistic, there also exist players who don't care about pets, only gold, and you may find it on the auctionhouse.
Happy hunting/holidays, Lumpy has a 3% droprate from a daily quest you can do each day for 15 days.
And don't go trading Frigid Frostling for Lumpy now, they are not a fair trade these days.