Well..............from the replies of some of the other "experts" on here, I guess the opinions of a guy with 38 years in the business as a High-End Architectural Millwork and Furniture Fabricator don't amount to much!
First and foremost, there is nothing wrong with melamine board for cabinet interiors as long as proper machining methods are used (Dado construction) and there is not a lot of moisture present ( one should not leave his GARAGE cabinets outside during a rainstorm). Melamine-coated particle board is a durable material and is used in residential as well as commercial applications regularly, and is the accepted standard...if you doubt this, I suggest that you refer to the Architectural Woodwork Institute's Quality Standards manual. What the manual will detail is what is and is not allowed in the construction of cabinets and millwork....Economy Grade, Custom Grade, and Premium Grade. It will detail what kind of construction methods are acceptable in these three grades of construction. It will also outline where fasteners are and are not allowed, as well as outlining what type and quantity of material defects are allowed.
If you are using the cabinets for storing parts for crawler tractors rather than reloading supplies and its related operations that the original poster stated, then plywood is the better material. If you want something that is even stronger, solid lumber panels will serve you better, or you could simply build the cabinets out of welded plate steel, the thicker the better.
What the original poster asked was what kind of methods and materials would be acceptable for his intended use. Be aware that he also noted that he was on a budget and did not have the funds available to use plywood for the construction. The suggestion to use Melamine for the counter-top surface was suggested by me in an effort to reduce the cost. Melamine will never have the wear resistance that Plastic Laminate does, but I have had work-tops in my Den for 7 years now, and the only thing noteworthy regarding wear is that the most used areas are more polished now than the light texture that they exhibited when new. I spend 5 hours daily at my computer sliding my mouse and keyboard around and it has not worn through the surface yet. While it may not be the best choice for a countertop, it is very reasonably priced, and is easily replaced when worn beyond the user's wishes. The cost to replace the counters is very reasonable as well.
I hope I haven't pissed in any of the "experts" cornflakes, but I believe I gave good information based on the original poster's needs, wants, and funding.
G'Night now....have a nice evening.
aloha