Viva Piñata

Buying accessories adds value to your pinatas, as well as their "joy level". If they are overjoyed, their value gets a little boost. If the pinata isn't overjoyed, purchase some joy candy and direct the pinata to it. It will eat the candy and the joy level will rise.

Sending them away for factory challenges also adds value. There are often challenges that pop up asking for "a single pinata, preferably a valuable one". When this happens, always send away the one you are trying to value-boost. When it's returned, it'll be worth more. I picked a pinata with a fairly high base value, maxed him out with accessories, then mailed him to myself and left him at the post office until the challenges popped up, then I'd retrieve him...send him away...then repeat the process. Keeping him at the post office keeps him safe so you don't have to worry about him getting sick, fighting with other pinatas, etc ;~)

You obviously need to do this with one of the more rare/valuable pinatas so you don't have to work as hard to get the achievement.

Additional tip from Elem3ntal80: Make sure to equip the Halo of Hardness (head), its by far the most valuable accessory.

Additional tip from Crimson Drfiter: If you get a 4,500 base coin pinata (Elaphinilla, Chewnicorn, etc.) then you won't even have to send them to challenges, just buy the most expensive accessories and you will get the achievement.

Additional tip from UzzBuz: This is probably a harder way of doing it, but if you are lucky it will help:

Very rarely, you will find wild card pinata's, think of them like shiny pokemon. They are worth 10x the base value of the normal version of the pinata. even something simple like a fudgehog would make the achievement pop right away.

Additional tip from M F a ii T H E: or you could get the dragonache and give it the required items and poof you'll level up about 2 times and get the achievement :).

Alternatively, if you are lucky enough to get a Dragonache and grow it to full maturity, you will get this achievement immediately after it matures because its base value is 11,000 coins.

See http://pinataisland.info/viva/Dragonache for details on acquiring an egg, hatching it, and raising it to maturity.

I used a Chewnicorn, which is level 9 (base value 4500) then gave him the most expensive accessory in each category, which took him to 11000 total value.

It's not too bad a Piñata to get, basically requiring you to breed Horstachios and a Gem Tree. He's needed for another achievement as well, so probably want him anyway.

I used a chewnicorn and put the most valuble item on it and when I was done the chewnicorn was worth 10800, achivement will pop right after you have put all the accessories on him!

I actually have a unique solution for this one:

You'll need a Bonboon, you get the Sour Variant after reaching Level 34 and when you reach Level 35, he'll visit your garden. You'll also need either a Syrupent, a Twingersnap or a Fourheads, direct one of them to the Sour Bonboon (recommend Twingersnap, is the one that worked for me) and they'll start to fight, if the Twingersnap wins, it will transform into a regular Bonboon.

Once you get him, buy him the most expensive accessories from Petula's shop, especially the Halo of Hardness, he'll be worth around 9,000 chocolate coins. Next, you'll wait for a Pinata Request from Langston, it has to be either a request for a Bonboon or better yet, a request for a single pinata of any kind, send the Bonboon with accessories to the box, and once he returns, he'll be worth 10,000, therefore, the achievement is yours!