While I can understand why you feel the way you do, your statement is wrong.
First, a large amount of tournament play is "Limited" - that is, you use sealed product to play with, rather than your own cards. There are different variations that test different skills (Booster Draft vs. Sealed Deck), but both are extremely skill intensive, and an individual's collection has no bearing on their performance.
In "Constructed" events - events where you play with cards from your own collection - it's often possible to outplay or outbuild the decks loaded with expensive cards at the casual or semi-competitive level. Tarmogoyf, a card that was selling for upwards of $50 on the secondary market, was an extremely powerful and efficient creature, but it could still be addressed by standard creature removal spells, such as Terror and Deathmark. Budget decks can often be around 90% as effective as the more expensive decks.
At the ultra-competitive level, the cost of cards caps out and everyone ends up spending around the same amount of money on their decks (probably around $500 if I were to buy all the individual cards on the secondary market). While this does create a barrier to entry, I've never heard people complaining about paintball or racing as "determined by how much they spend on the game." Most hobbies have equipment, if you're looking at competitive level Magic, players invest in their decks, but everyone caps out on cards so money isn't a determining factor.
Finally, players will often loan and borrow cards among their friends, further lowering the cost of acquiring cards to create a deck.