More time was obviously spent on the design of the item and it will look nicer overall. This is probably the most judgemental factor because it really boils down to if it appeals to you. Scarcity is probably the least understood factor. Most people do not seem to realize that just about everything is mass produced. This means tens of thousands of the item were made or even hundreds of thousands in some cases-Even most limited editions are measured in the thousands.
Time is the biggest factor for weeding out the numbers.
Moms throw things out, toys wear out, fragile items break. So the older an item is usually the scarcer it is. Beware of limited editions too. Unless it is a numbered edition and the total number made is listed this term means very little. In todays market most collectibles are sold as limited editions when in fact the only limit on them is how many they can crank out in their time limit.