... I'm honestly surprised at the pushback I'm seeing in this thread. ...
Not pushback against asteroid mining. Pushback against the idea that you can spot a gold vein in an asteroid from several AUs off. At least I think that was what you were saying. Mapping the asteroid field is the easy part. Heck, the scouts have likely already done that just in the course of making sure nothing's on a path to wreck the local mainworld. Buy their data.
If you mine MegaTraveller, gold prospecting is actually not that difficult. There's a densitometer in that game. Per the MT Referee Manual, "A densitometer with any penetration beyond surface can give a density map of an object's interior to the penetration depth shown." Densitometers capable of a density map show up at TL 11 with 1 meter penetration. By TL 15 they're mapping to a depth of 1 kilometer. Pricey - the TL 15 high penetrator is Cr1,500,000 - but well worth the money. If you're on a budget, a low penetration model at TL15 costs Cr205,000 and gets you 250 meters depth.
However, you've got to be there at the asteroid to do it. It's not something you can do from great distances. Our local example of an asteroid belt is on the order of a couple to 4 1/2 AUs out, the decent sized bodies average about 600,000 km apart, and it has between 700,000 and 1.7 million bodies of 1 Km or larger. So, you go to an asteroid, you do your densitometer scan, you spot the ore bodies - I don't know about the other metals, but gold has this nice thing about liking to show up in elemental form, so it should stand out pretty nicely on the densitometer. Probably easier to find than those metals that get tied up in rocky chemicals.
Now you do the mining. Same as any ground-side mining with the advantage or disadvantage of being in vacuum and zero G, and you've got tech like lasers to help with it. If you've got a Seeker, which is the classic mining ship, you've got a MCr25 ship (which likely already has a densitometer since it's a remodeled scout/courier) that you're paying Cr104,000 monthly for, plus your fuel and life support costs. Figuring from that Cr7054/Kg quote, I figure you need to recover a bit more than a half kilogram per day to break even. They measure gold mining in grams recovered per ton, if I read the Wiki right, and the good stuff back in the day was in the 20-30 grams per ton range; we're closer to 10 nowadays. So, you're mining something on the order of 25 tons of rock per day to bring up enough gold to break even. Maybe less, 'cause you've got a better picture of where the veins run than we do nowadays, but you've still got to get at it.
However, Seeker's got two 10 dTon ore bays; unless you've got money for the kind of machinery that will separate the gold from the rock, and haul the machinery out with you in your Seeker, you're filling up your ore bays with 270 cubic meters of rock - call it 800 tons of rock - and then hauling it to a processor to recover 20 kilograms of gold, which pays for your ship that month and gives you a very nice Cr35,000 to divide among you and your crew (up to 4 persons in the Seeker), assuming of course your find was reasonably rich and you could dig up 25 tons of rock a day. More lucrative if we assume you're getting a higher percentage of gold or can dig up rock faster, less lucrative if we think you're digging up less than 25 tons of rock a day or your find is leaner. You could get a bigger ship, but it still basically comes down to how much you and your crew can dig per day and what percentage of that is gold. Of course, there's be other ores as well, but I don't know how to figure those, how likely they are to be in a particular patch of rock, or what value you're likely to get from them.
Short form is: the guy in his Seeker can probably make a very nice living at it if we set the starting assumptions reasonably generously, but he's not likely to get rich. The folk who get rich are the big boys who can hire more crew and haul the fancy machinery out to the site to do their processing on-site rather than flying back to wherever the processing station is, since distances in the belt are likely to be large.