Hi,
Anyway Keukenhof is a very nice garden to visit; one of the best in the world. I know, because I stayed near Keukenhof for four years of my life.
The myth that F&E is more expensive continues to persist. Yes, if planned badly, it will be more expensive. But if planned well by a savvy traveller (like me haha), then it will always be cheaper. For example, in 2005, under SGD 3k per person, everything inclusive, for 19 days in France, 4 persons travelling together:
http://rtan.net/France/
And the cost will be about the same now because although air fares are higher, the Euro is weaker.
For our F&E trip in 2009 of which you saw the wonderful pictures (it was 16 full days, 15 nights), the cost was just under SGD 4k per person for my wife and I, everything inclusive. And this time we went a little more luxurious; decent accommodation (no Formule 1 or ETAP, minimum IBIS standard), at least one meal in a restaurant per day, DIRECT flight on Qantas from SG to Frankfurt (no lengthy stopovers and Qantas was no worse than SQ in our experience), and of course it was much more romantic as well.
What I certainly agree with you is that it takes a lot more time and effort to plan; that's what you are paying the tour company extra for. But of course as you mentioned, you get to see a lot more going F&E.
The other thing about planning F&E is, like with everything else, practice makes better. The first time seems hard, subsequent times are a lot easier and faster; now I plan F&E trips in a matter of days, not weeks.
Anyway there is no right or wrong choice; each has its pros and cons. What you might wish to consider is to extend your tour to do a few days F&E at the last destination; then you get some freedom and can explore on your own.
Hope you have a good trip, get a good tour guide, and have good and considerate travel companions. And of course, enjoy Keukenhof!
PS: Don't step on the flowers, as we saw some stupid inconsiderate PRCs do as they were trying to take photos; they didn't even seem apologetic about destroying the pretty flowers. I should have scolded them on the spot.