As usual, I think this thread
has some relevance to this question. I sincerely want to avoid seeming unfriendly, but if I lack patience for these types of questions, it's usually because someone is out to make a buck and is taking advantage of our eager-to-help community by using them as their appraiser. I'm cynical that way. Not accusing you of anything, combattank, just speaking generally about my own mindset in the hopes of explaining that any perceived crotchetiness on my part is brought about by slick profiteers, not honest LEGO-loving folk.
The thing is, "value" of a LEGO set in the context of using it and enjoying it
is really up to the individual. With that in mind, there is plenty of information available online that can tell one what he/she needs to know about set inventory, instructions, the average price of sets of comparable size, etc. If one is only curious as to what one can get for it on eBay, I suggest they do a search for the item there. To answer your question, I think there is a bit of a mark-up for Architecture sets because of their "premium" nature and specialty decorated plates. I would think, given the relative ubiquitousness of the part/color selection in most architecture sets, that you could probably piece together the sets via Bricklink/Pick-a-Brick for cheaper than the retail set. Then again, that's not taking shipping/handling charges into consideration. For a real answer to that question, some research is required. Just in case you weren't aware, you can build wanted lists in Bricklink based on an individual set's inventory. If you haven't done that yet, you might try it to see how likely you'd be to acquire the parts you need in as few shops as possible to cut down on shipping.