Answer: Heck no, quite the opposite in most cases! That probably comes as a big surprise to many folks.
First of all, when travelling ultralight you typically bring less gear, which means you've already spent less. No $35 camp chair, no $15 "backpacking pillow", no Lexan dinner plates, etc. If you've already bought the stuff, you may decide you don't need it anymore and can sell it. Or heck, just keep it around for an ocassional decadent 35lb weekend! *8-)
Also much of the lightest gear is actually far LESS EXPENSIVE than their heavier cousins!
Sure, some ultralight items (titanium pots, high-end 775-fill down bags) are premium items at premium prices, but much of the gear you'll want for ultralight backpacking really is less expensive. (Though sometimes you may need the performance and features of heavier and/or more expensive gear, such as when snow camping, etc). At the very least, most of the lightest gear isn't any more expensive than the heavier stuff.
(Sorted by price, # = lightest item(s))
Cascade Designs LiteFoam Thermarest 3/4 Length -- $48, 22 ozs Cascade Designs Z-Rest Mattress 3/4 Length -- $19, 11.5 ozs # Cascade Designs Ridgerest Closed-Cell 3/4 Length -- $12, 9 ozs
MSR Whisperlite -- $53, 14 ozs (11 fl.oz. fuel bottle - $8, 3 ozs) # Mini-Trangia No. 28 -- $25, 11.5 ozs (incl. pot/lid! But not fuel storage) # Esbit Pocket Stove -- $10, 3 ozs (fuel tabs 0.5 oz each, 2 per liter boiled)
Arc'Teryx Bora 60 Pack '98 -- $290, 91 ozs, 4030 ci REI New Star -- $200, 92 ozs, 4600 ci Mountainsmith Mountainlight 4000 -- $195, 50 ozs, 4000 ci Lowe Contour ND II Sirocco -- $160, 90 ozs, 4200 ci # GoLite Breeze -- $120, 11 ozs, 4200 ci (rucksack)
So what about those titanium pots and high-end 775-fill down bags? Are you stuck paying through the nose for them? Heck no! Well, maybe for the titanium.... *8-) Actually, REI sells the Evernew 1.3L titanium pot for $40, vs. $17 for the 1.1L MSR Stowaway pot - a premium to be sure, but hardly devastating. Factor in all the money you saved buying your other ultralight items and you're still WAY ahead! (Assuming you decide the titanium pot is worth it for your needs.)
But back to the point at hand. Believe it or not, you can buy high-end ultralight sleeping bags and technical clothing for 25%-60% or more off Suggested Retail! The trick is knowing when and where to look for it.
Every year (around January?), REI stores have a "slightly used gear" sale. It's only open to REI members (I believe), and it features gear that's been returned by customers and has *just* enough wear on it that it can't go back on the racks/shelves as new. Bargains everywhere! You figure quality gear should last for many years, right? So if it's already been worn a month or two, but seems to be in good shape, you walk away with solid merchandise at steep discounts! All the really good stuff is usually snapped up within minutes, so it tends to be a bit of a feeding frenzy.... Other discount outlets exist out there too. Ask around, check it out!
Another excellent source for finding high-end gear at significant markdowns are outlet stores like REI-Outlet.com and the Sierra Trading Post. They buy up gear from major manufacturers that's being closed out (last year's models), is overstocked, or has minor cosmetic blemishes that don't affect the functionality or durability of the item. For that, you get all kinds of stuff at 35%-70% off! Sleeping bags and anoraks from Marmot, clothing from The North Face, snowshoes from Tubbs, backpacks, plus other goodies. The drawback is that stock is limited to what's on hand (no backorders), and popular sizes/colors tend to go fast. If you don't mind some odd colors in your wardrobe, you won't have a problem. *8-)
I've picked up great bargains from Sierra Trading Post and REI Outlet. For snow camping, I picked up a Marmot Couloir down bag (775-fill) w/ optional DryLoft shell for nearly $175 off the next cheapest price I could find. My Marmot Arroyo 775-fill down bag (only 28 ozs!) was also about 30% off. I've grabbed snowshoes, a mountaineering anorak, expedition-weight long underwear, etc, all at steep markdowns. But I had to be patient and wait. They don't keep a regular inventory, remember. Stuff comes, stuff goes. Your mileage may vary.
Ultralight backpacking not only saves you weight, it can actually save you money!