You should consider using Blocknet.

Rather than hiring a team to build a decentralized exchange from scratch, I would suggest a different approach. www.blocknet.co is a fully open source, fully functioning decentralized exchange and it's completely white label on the sense that you can build on top of it whatever you wish. It won't ever cost you a single dollar to use it and you can charge your own fees on top.

There is nothing to stop you building a DEX website on top of the Blocknet protocol. The Blocknet API is extremely comprehensive, and has all the commands you would expect to get the orderbooks, place orders, cancel orders etc. This powerful API is one strong point of the platform. The other being, it's truly decentralised in every sense of the word - no KYC, decentralized orderbooks, no custody of user funds, no centralized smart contracts, coins which are compatible with the protocol are automatically compatible with no listing fee etc.

If you're interested feel free to PM me or reach out to the Blocknet team on the discord: https://discord.gg/2e6s7H8. And if you're interested in seeing some live orders on the blocknet protocol check out https://blockdx.co

Cheers