When is the $10 Assembly Fee Worth the Price?

If it has moving parts you have to put together...pay the 10 bucks..
If is is so tiny you need magnifying glasses to put it together, pay it.
Flat box?  Depends.. because cheap bookcases in flat boxes are easy to assemble and gratifying if a kid is doing it.  Very large boxes may require discernment!.
Let me tell explain...when the three girls were young , my husband and I spotted this huge, beautiful doll house.  Oh my goodness..the girls are going to love playing with it!  We could hardly wait for Christmas, just so we see their faces when they saw it.  So we bought it.  It was in a large flat box...meaning we had to assemble it.  OK, the husband is up for it...we have to wait until the last minute though ( Christmas eve) because it is too big to hide!  So, off I go to work the 3rd shift in the hospital, kissing my husband good bye and wishing him luck getting the presents under the tree...., little did we know that was the least of  his worries.  Putting a 5 foot dollhouse together the night before Christmas is completely absurd!  And this wasn't a barbie doll house where the dolls were taller than a pencil, this was like Polly Pocket size....a mansion doll house for miniature dolls. And it was a whole house...kitchen and appliances, 4 bedrooms, fully furnished, the dining room had little dishes for the hutch...all needing to be assembled.  I came home at 7am (got off early) and there he STILL was ... but  now he  made it to the sticker part... where he puts the stickers on the walls that are supposed to be wall decorations, like pictures, tiny wreaths,  but the stickers were  now getting more crooked or very slanted, especially in the family room ....  the lesson here is: do NOT assemble a doll house yourself! 
Lesson #2;  Avoid do it yourself assembly when it involves multiple moving parts.
Well, by now we are a little more experienced...and I see this green machine in Target...it is like a big wheel, but much cooler..gears, things like that... which should have definitely been a red flag. The green machine is in a large box, not flat.  One of the high school boys who was forever hanging out at our house drooling over our daughter, was kind of tech guy, always tinkering with things, building things....so we asked him if maybe he could put the green machine together. Oh, sure, that would be fun.  So she watched him, pretty much in silence because he had to concentrate on the 110 plus screws  for about 3 hours.  Well, he was only a high school kid..but the finished product had some deficits... the seat was not right ...couldn't pinpoint exactly what was wrong, but the seat was just not right, it was backwards or something like that.... but the worst part was the steering ... when you turned the steering wheel to the left, the wheels when right, when you turned the steering wheel right, the wheels went left...  I was afraid the kids minds would get messed up if they rode it.  .
So, there you have it...isn't the age of electronics is easier, ?!