If you defense is to blow 230k of your own funds on a project that was said to cost [at least?] 10x what was necessary at 460k estimate, then perhaps you need to take a step back and realize someone might be trying to rob you specifically for 180k in services, on top of the additional $230k. You don't strike me as the type who is developing it from your own mental prowess given your own cash infusion, but a business type who recognized the value the project may bring, who may be getting screwed over bigly by a firm.

If you are familiar with coding, then try to set aside a week or two for yourself, to do one your own. From there, give the dev/firm hell and negotiate a for better price. You likely could threaten the firm to train a dev in house, may maybe pump out a new chain a week or faster, if they don't acquiesce to more reasonable pricing.