First of all, welcome to the boards.
Man, that's the pits about your table & situation.
I don't know anything about Colorado's climate (I have the opposite climate--humidity city). I googled: Colorado furniture dry air. I glanced the results & it seems that what the guy told you could be true. I think he should have told you all that WHEN YOU BOUGHT the table though...issued a disclaimer of sorts, for Colorado residents.
As far as the other cheaper furniture being fine & the expensive piece cracking: it's the nature of the beast. Wood is very sensitive to moisture changes...contracts with dry air & expands with humidity. It's normal for wood.
Veneer is a thin slice of wood that is glued onto a substrate of some type. It's more inexpensive to produce. The substrate & the sliced veneer don't "move" the same way that a solid wood dining table, like Montego, would.
Montego is more expensive to make. It has a large solid wood top, but that solid top consists of several solid planks of solid wood that are laminated or glued together. Each piece would move in response to dry or humid air. The problem you are having is called delamination. Delamination is when previously glued together pieces of wood separate. It's usually caused by extreme swings in temps/humidity/moisture.
I
think that the placement of pieces is important, when the table is constructed. What I mean is, if they glued two pieces together with the grain running the same way on each, they might move the same way. If a table were glued together with pieces of opposing grains, they would not move the same way & you're left with a crack. I'm thinking opposing grains would mean more potential for problems, like you're having. And I think matching grain lamination is better and higher quality construction. A wood craftsman that makes custom kitchen cabinets or builds furniture (check your yellow pages) would be very knowledgeable on the subject could tell you more about this aspect. I might be have it totally backwards.
(My first job out of college was customer service for a nat'l furniture manufacturer that made outdoor furniture. We had one item in our line that consisted of laminated solid wood. It's been many years since then. It's hard for me to remember all that stuff about the grains & lamination. I either have it right, or backwards.)
In any case, I have to wonder the same thing as you: Why would PB sell their furniture in a climate where is would be normal for it to delaminate? Do y'all have central heat & air conditioning systems in your homes? Maybe the better question is: Is a humidifier part of the typical home's checklist in Colorado..the norm? If a humidifier is not the norm, it seems to me that their customer service dept would be absolutely overrun with claims from Colorado residents wouldn't it?
As for repair or replacement.... I don't blame you for being wary of the repair. How will it look? Will it happen again? If so, what happens the next time? Will the humidifier definitely solve the problem? Sounds like he's saying that if you get the humidifier then the repair or the new table would be fine & it wouldn't happen again. Wonder if he'll put that in writing!
You really need some knowledgeable help...not pitiful "can't remember" me. You need help from someone unbiased who can tell you if your table was constructed properly (grain direction/delamination thing that I might have backwards). You need to find someone unbiased who can confirm/debunk the humidifier being a necessary thing in your climate, if you have solid, laminated wood furniture. I'd pull out the yellow pages & look for a custom cabinet maker or custom furniture maker. I'd call them & tell them your situation. Tell them you are desperate & seeking advice & hopefully they will give you some. Most people in that line of work are people that really know & love their craft. They might enjoy sharing their knowledge & helping you out. Maybe you could pay them a visit & ask if they'll look at your pics, or have them come look at your table. You can always offer to pay them for their time. It might be advice well worth paying a little for.
Good luck!