From what we understood, the daily wages for guides are almost always fixed across the board, so really we were just negotiating to lower the (huge) cut that the agency would collect. Our accommodation was included in the price, as were bus tickets to the trailhead and all the required trekking, conservation area and restricted area permits.
Once we had our trek sorted out, we went on a bit of a shopping spree. There are endless options for buying gear in Thamel, ranging from dingy, dusty one-man knock-off operations to brightly-lit and well-stocked showrooms carrying (legitimate) international brands. We shopped around a lot, and were happy to look for knock-off or unlabelled gear, as we really only needed it to last a couple of months. Much of the gear is locally-made, even if it claims to be "The North Face", and if you look hard enough, you can find excellent quality gear for very reasonable prices.
We did find that the prices varied enormously - from one store to the next, we might get quoted double the price for an item of almost identical quality. Some shopkeepers were happy to bargain, while others wouldn't even begin to budge. Quite a few people were confused by Pravin at first and thought he might be Nepali (until he spoke, that is), so often with a few laughs and a bit of bantering, he was able to get a deal much closer to the "Nepali price".
After two days and many, many stores, we finally came away with two -10°C down sleeping bags, an additional down jacket for me, gaiters for the snow, a long-sleeve shirt and new trekking pants for me, fleece pants for both of us, snow mitts, batteries, toilet paper, maps, water bottles, hand sanitizer, and most importantly, a large supply of chocolate bars for trail snacks.
Our knock-off/off-brand gear ended up working out perfectly well for us. The sleeping bags were an especially good deal, as they kept us toasty warm for all but one of the 42 nights we spent on the trail! Once we returned to Kathmandu in January after all of our treks were complete, we were able to sell back much of what we didn't need any longer and come away with about $65 of the $180 total we had spent on trekking equipment. Everything else, including some other clothes we no longer needed, was able to be donated to the Porters' Welfare Program at the Kathmandu Environmental Education Project. We didn't make it to the KEEP project office until after our treks, but we would 100% recommend anyone preparing for a trek in Kathmandu to stop by and make use of their excellent resources.