Is this a grammatically correct statement?

"I don't have much experience with zoom lenses and I always considered them more of toy lenses. The only one that is really worth buying is the Nikon 70-200mm f/2.8 but it is expensive."

Yes that's fine, but instead of "much" I'd you "many", because some people consider much as slang.
And, because "it is expensive" is an opinion (as compared to a millionaire), I think you should use "Although, it is quite expensive". Because it shows vocabulary knowledge.
Hope I helped!

No. The first sentence should read considered them more Or Less toy lenses.

I cleaned it up for you.
"I don't have much experience with zoom lenses because I have always considered them more of a toy; the only lens that is worth buying is the Nikon 70-200mm f/2.8, but it is expensive."