I fully get your worries and I'm sharing them.

However I don't think right now, bots buying 10$ spellbooks to try and milk rewards is a viable strategy. Instead, Splinterlands will more likely be milking money from them giving mostly potions and soulbound reward cards in return unless a bigger investment is followed.

Speaking for myself in case I was a new player, 10$ just to get going probably would be the absolute max. A higher price that includes some packs would put me off for sure.

What I would do to fight bots is to bring back collection power in Wild so it's impossible to get rewards with little to no investment.