But there is a ceiling to how much "budget" you can assign to the game... the "best" decks for most tournaments are either almost unchanging over time (the expensive, Legacy decks) or are limited to a few hundred quid (Standard Decks). It's also fair to say that as soon as you move from even remotely casual play to basic competitive play, EVERYONE has the cards they need - while some players might have had to pay out some money to meet that minimum competitive level, there are few to zero players who sit at a table playing a "cheap" deck of cards and suffering from a statistical disadvantage - everyone gets what they need, so the "higher budget more options" argument only applies to maybe 20% of players on the lower end of the competitive scale. Once you enter the competitive realm, the playing field is very flat in terms of budget, and mostly comes down to information warfare (research, preparation, networking).
And if you're good at the game you will be acquiring cards for free from prizes at a very fast rate - the best local players, who do NOT make it to the Pro Tour, pay little to nothing to play the game... they win the majority of the cards they need, and can borrow others from traders/stores in return for promoting the stores. The "cost" of the game to newer or weaker players is actually subsidising the better players in many ways - although the money changes hands in ways completely different from poker, it results in a fairly similar outcome (admittedly with much smaller amounts).
Finally, the aspect of the game known for being most skill-intensive is called "Limited" where everyone pays the same price to play and plays with cards provided, rather than cards they have bought/collected - here financial muscle is no advantage at all, and this form of the game is more enjoyable and rewarding to many players.