Nice game, unfortunately too much depends on luck... and I strongly believe that getting to $20M is just a lucky shot. I spend some time building spreadsheets and analyzing strategies and came out with few conclusions I'd like to share.
I've took a median price over few games, and from there I've calculated where are the best buy/sell price spots taking into account that you pay 15% of tax and you want another 15% of your trade margin as minimum. So table sums up list of commods, sample name (that changes each game), max buy price, median price, min sell price:
| # | Mid Price | Buy Max | Sell Min |
| 1 | 150 | 127 | 172 |
| 2 | 200 | 170 | 230 |
| 3 | 250 | 212 | 287 |
| 4 | 325 | 276 | 373 |
| 5 | 450 | 382 | 517 |
| 6 | 600 | 510 | 690 |
| 7 | 750 | 637 | 862 |
| 8 | 1100 | 935 | 1265 |
| 9 | 1500 | 1275 | 1725 |
| 10 | 2200 | 1870 | 2530 |
Following these prices guidelines will get you solid results usually in Few millions. Rest is luck, as some events can suddenly triple your account, or turn it to zero.
(Remark - I've check also the distributions of prices vs the the originating planets and the stocks size so it really does not matter to which planet you are flying next, it does not matter for the the stock sizes or has no real impact on the prices - saddly).
Anyways, Each planet Entire market total value is max $1M - $1.5M so really hard to get your truck to be full of goodies get to value of $20M w/o any extra ordinary event.
When you suddenly after lucky event get in few $M in cash usually you can buy out entire planet one after another and then the game balance suffers horribly... the strategy then turns into buy all everywhere, don't sell anything, fly around and keep fingers crossed for next high price event to fire so you can sell commod for couple $K a piece, then buy all again and repeat.
I dislike that randomness to be honest. Anyways, had some fun on figuring this out... cheers!