There are a fair number of threads on this topic.

First, the term road bikes encompasses touring bikes, but not all road bikes are designed to work well for loaded touring -- wheelbase too short, gearing too high, handling not as stable, chainstays too short, and wheels not strong enough. So if you are looking for a new entry level bike that's designed for touring, the Windsor Tourist probably is the cheapest option for a new bike at $599, although there are a number of reports of the rear wheels having spoke breakage issues. But I don't know if that's a systemic problem now (or if it was ever).

The 2 bikes you mention are not really designed for long distance loaded touring. Flat bars for most are bad for long days of riding (not enough hand positions) although bar ends can help a lot, and the gearing isn't low enough on either of those two bikes for loaded touring on hills, in my opinion. Chain stay length on the Windsor probably is too short, will result in your heels striking your panniers. Don't know about the quality of the wheel build

If I had $400 and no more to spend on a bike, and if I wanted to use the bike for loaded touring, I would look for a mid 90s rigid mountain bike like a Trek 970 or the like, put on narrower tires, and put on bar ends or trekking bars. The wheels would be strong, the gearing would be low, and they are rugged bikes that ride well and have a touring geometry. You can find them in the $100-$175 range where I live. The suggestions of dengidog are good, too. I picked up a fantastic touring bike for $120 at a bike swap a few years ago and am using it as my primary bike.

Yes, you can tour on any bike, but it's nicer to tour on a bike that will work well for the purpose.

Now if what you want is to simply ride unloaded, then many road bikes will serve that purpose, probably the Wellington 3.0 would be OK, assuming the wheels are OK. But you asked here about coast to coast touring, and that narrows the field.

One other thing: don't assume that bike shops "overcharge like crazy". What's your basis for that statement? Do you know how to evaluate the quality of a bicycle and how it has been assembled? Most people who have been bicycling for a while will tell you that a good bike shop offers **a lot** of value for what they charge.