Hi Caio,
This is Bogdan from Romania.
I'm a mechanical engineer - specialized in the industrial robotic field, 3D designer and modeler (from time to time and some projects I could make the functional prototype too).
I'm doing product design, industrial design, reverse engineering, ideation, etc.
I have over 15 years experience working on various systems/devices across multiple industries, from concept to launch.
1 - my bid is higher because i know what it means to design such machinery... (a lot of experience with all kind of machineries in very harsh conditions/environments)
2 - the injection machine you showed in the attachments are doable, but will need some improvements...
3 - before start designing will be necessary to discuss about the machine parameters (injection volume, axial travel, heating element, cleaning procedure, mold fixtures, etc, etc)
Regards
Bogdan