“Yeah, here I'm making a simple spice rack out of some purple heart and cocobolo I just had lying around.”
I'm pretty pleased already if I can get my hands on a few scant planks of walnut at a passable price here in the Netherlands.
Every sawmill/timber merchant/whatever near me basically sells fences and roof trusses.
For example: Home Depot (which is a national chain of home improvement stores) generally stocks pine, red oak, some yellow poplar (which is not actually a poplar, but I digress), and sometimes something they'll call mahogany (which almost certainly isn't Swietenia anything) . That is about as good as you'll find unless you go somewhere that specializes in hardwood lumber. Unfortunately, some of those don't do retail sales.
For US readers in the northeast, Highland Hardwoods and Northland Forest Products both do retail sales. Northland is more focused on North American wood, though they stock FSC certified mahogany. They're about 10 minutes from each other about an hour and 15 minutes from Boston (usual traffic caveats apply), where I suspect a lot of people from HN at this time are located.
On the other hand, I always see Europeans complaining that American houses are made out of wood and aren't designed to last like good concrete or brick European houses... Well now you know why. No need to double the cost of materials for most houses.
Smaller pieces will typically cost less at the lumber yard, and it also makes it easier to work with salvaged wood -- you no longer need to find big pieces to salvage, you can salvage a lot of little pieces and build them up.
Also note that salvage isn't just dumpster diving -- at auctions and sales you can find large things people made for particular purposes that no one wants, and break them down for raw materials. I've picked up a couple hundred dollars of dimensional lumber for a $5 bid before because it was in the form of a 9 foot tall viewing platform for refereeing volleyball games.