To get MTM that cheap, you'll have to go to one of the traveling tailors who frequent London hotel suites, AND order one of their bottom-of-range fabrics. (Don't be overly beguiled by Super numbers, btw, as not all fabrics are created equal, whatever number supposedly indicating fineness of fibers might be attached to them, perhaps as a marketing gimmick. A cheap Super 150s, probably spit out by a high-speed loom, is not somehow 'better' than a quality Super 100s--in fact it's almost certainly worse.)
I've been this route, and believe me, the $500 I blew would have been much better spent on a Hickey-Freeman from eBay, Bluefly, or Filene's Basement, or even on a BrooksEase (a suit I happen to think is pretty darn good for the money), than on the crummy but "made to measure" garment I wound up with after having to have the tailor completely remake it at the cost of six weeks' delay.
If you want lower-priced MTM and want it done decently, you had best make up your mind to go to Mr. Ned, or LS Menswear, or English-American Tailoring, and be ready to spend something more in the neighborhood of "one large."
You can get a Coppley MTM with a good basic fabric with a half canvas construction for about $800. John H. Daniel starts out around $900 or so I believe, and that is for a fused garment. A MTM full canvas suit will be in the $1500 range.
I am currently spending around $600 a time for an (allegedly) fully-canvassed pick stitched 2-piece suit with extra trousers from Ravi Tailors, with a spare pair of trousers, made from their entry-level fabric collection ("Classic.") Apart from a few minor quality issues (brace buttons missing or oddly placed, not all the buttons are shanked properly) I am quite satisfied; construction and fit seems fine to me, but I am not as discerning as many here. It works for me on my budget but would not be for everyone.
The first (1 button s/b peak, spec. as above) was ordered online (came to about $500) and was not exactly right (which I attribute to my measurements rather than any problem their side) but close enough. For the second (1 button s/b notch) I saw a visiting tailor, wearing my first suit. We discussed and agreed how we would change the figures for that order (I had to push a little to agree a shorter length for the jacket and less break on the trousers, but we readily agreed that there was too much fullness in the thigh and that the cuffs were too wide) and I was pleased, overall, when it arrived. Being happy with the measurements by now, I decided to diversify and ordered a 6x2 d/b in a solid grey. This has also turned out quite well and I will probably get another, this time in a weightier fabric for the winter, with slightly broader lapels for that 1940s look.
NB that the Classic range is dominated by wool mixes, but there is a small but growing selection of pure wools from Far Eastern mills. For products of known mills you have to go up several ranges.